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DANIELA FONTANA
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Dipartimento di Scienze Chimiche e Geologiche - Sede Dipartimento di Scienze Chimiche e Geologiche
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Pubblicazioni
2024
- Multi-source detrital contributions in the Po alluvial basin (northern Italy) since the Middle Pleistocene. Insights into sediment accumulation in intermediate sinks
[Articolo su rivista]
Demurtas, L.; Fontana, D.; Lugli, S.; Bruno, L.
abstract
Integrated stratigraphic-compositional studies on alluvial successions provide a valuable tool to investigate the provenance of detritus in multi-source systems. The Po Plain is an intermediate sink of the Po-Adriatic source-to-sink system, fed by rivers draining two orogens. The Alps are characterized by extensive outcrops of plutonic-metamorphic and ultramafic rocks to the north-west and of Mesozoic carbonates to the east (Southern Alps). The Northern Apennines, to the south, are dominated by sedimentary successions. The Po River flows from the Western Alps to the Adriatic Sea, interacting with a dense network of transverse tributaries that drain the two orogens. Stratigraphic, sedimentological and compositional analyses of two 101 and 77.5 m-long cores, recovered from the Central Po Plain, reveal the stacking of three petrofacies, which reflects distinct provenance and configurations of the fluvial network. A South-Alpine sedimentary input between MIS 12 and MIS 10 is testified by petrofacies 1, characterized by carbonate- and volcanic-rich detritus from rocks exposed in the Southern Alps. A northward shift of the Po River of more than 30 km is marked by a quartz-feldspar and metamorphic-rich detritus (petrofacies 2), similar to modern Po River sands. This dramatic reorganization of the fluvial network likely occurred around MIS 9-MIS 8 and is possibly structurally controlled. A further northward shift of the Po River and the onset of Apennine sedimentation in the Late Holocene is revealed by petrofacies 3, rich in sedimentary lithics from the Apennine successions. The results of this study document how compositional analysis, if framed in a robust stratigraphic picture, may provide clues on the evolution of multi-source alluvial systems.Inferred palaeogeography of the central Po Plain, deduced from compositional variations of core sands, during: (a) MIS 12 and MIS 10 (petrofacies 1). (b) MIS 5-4 (petrofacies 2). (c) MIS 2 (petrofacies 2). (d) The early Holocene (petrofacies 2). (e) The late Holocene (petrofacies 3).image
2024
- The transition from normal marine to evaporitic conditions recorded in a cold seep environment: The Messinian succession of Northern Italy
[Articolo su rivista]
Conti, S.; Argentino, C.; Bojanowki, M.; Fioroni, C.; Giunti, S.; Kremer, B.; Fontana, D.
abstract
2022
- 3D Engineering Geological Modeling to Investigate a Liquefaction Site: An Example in Alluvial Holocene Sediments in the Po Plain, Italy
[Articolo su rivista]
Meisina, C.; Boni, R.; Bordoni, M.; Lai, C. G.; Bozzoni, F.; Cosentini, R. M.; Castaldini, D.; Fontana, D.; Lugli, S.; Ghinoi, A.; Martelli, L.; Severi, P.
abstract
Liquefaction-induced surface manifestations are the result of a complex geological–geotechnical phenomenon, driven by several controlling factors. We propose a multidisciplinary methodological approach, involving engineering geologists, geomorphologists, sedimentologists, and geotechnical engineers, to build a 3D engineering geological model for liquefaction assessment studies. The study area is Cavezzo (Po Plain, Italy), which is a municipality hit by superficial liquefaction manifestations during the Emilia seismic crisis of May–June 2012. The site is characterized by a Holocene alluvial sequence of the floodplain, fluvial channel, and crevasse splay deposits prone to liquefaction. The integration of different geotechnical investigations, such as boreholes, CPTm, CPTu, and laboratory tests, allowed us to recognize potentially liquefiable lithological units, crucial for hazard assessment studies. The resulting 3D engineering geological model reveals a strict correlation of co-seismic surface manifestations with buried silty sands and sandy silts within the shallow 10 m in fluvial channel setting, which is capped and laterally confined by clayey and silty deposits.
2022
- Evolution of the Po–Alpine River System during the Last 45 Ky Inferred from Stratigraphic and Compositional Evidence (Ostiglia, Northern Italy)
[Articolo su rivista]
Demurtas, L.; Bruno, L.; Lugli, S.; Fontana, D.
abstract
The stratigraphic and compositional study of three sediment cores recovered close to the Po River near Ostiglia provides clues on changes in fluvial dynamics at the transition from the last glacial to the present interglacial. Upper Pleistocene units are dominated by sands with high content in volcanic lithics, denoting high sediment supply from the south-Alpine fluvio-glacial tributary system. The Early–Mid Holocene unit, peat-rich and barren in fluvial sands, results from low sediment supply and waterlogging, encompassing the maximum marine ingression. The Late Holocene unit, characterized by fluvial-channel sands with lower content in volcanics and relatively abundant metamorphic lithics, records the Po River sedimentation since the Late Bronze Age. Late Holocene sands show a lower content in siliciclastic lithic fragments (supplied mainly by Apennine tributaries) compared to modern Po River sands. This distinctive composition could reflect the diversion of Apennine sediments into a southern Po River branch during the Late Bronze Age and into an Apennine collector flowing south of Ostiglia during Roman times and the Middle Ages. The integrated stratigraphic-compositional methods used in this study permitted to reconstruct the major climate-related changes in sediment dispersal and may be potentially applied to other alluvial and coastal settings.
2022
- Liquefied sites of the 2012 Emilia earthquake: a comprehensive database of the geological and geotechnical features (Quaternary alluvial Po plain, Italy)
[Articolo su rivista]
Minarelli, L.; Amoroso, S.; Civico, R.; De Martini, P. M.; Lugli, S.; Martelli, L.; Molisso, F.; Rollins, K. M.; Salocchi, A.; Stefani, M.; Cultrera, G.; Milana, G.; Fontana, D.
abstract
This paper presents a comprehensive geological and geotechnical study of the whole area affected by liquefaction following the 2012 Emilia earthquakes, including all the available information from the field reconnaissance surveys, in situ tests, and laboratory analyses. The compilation was performed at 120 liquefied sites to verify and validate the reliability of liquefaction charts in alluvial sediments, and to assess liquefaction induced by the 2012 seismic sequence in the Emilia plain. The results reveal a wide range of grain sizes (from clean sands to sandy silts) and compositional characteristics (quartz-rich to litharenitic) in the 2012 ejecta, and show a strong relationship between the liquefaction and stratigraphic architecture of the subsurface. The availability of in situ tests at the liquefied sites makes it possible to verify and validate the reliability of the liquefaction charts in alluvial sediments with respect to the real observations. For the analyzed Emilia case studies, the use of non-liquefiable crust provides better estimations of the liquefaction manifestations when coupled with the thickness of the liquefiable layer rather than with the liquefaction potential index. Altogether, this work makes available to the international scientific community a consistent liquefaction database for in-depth earthquake studies.
2022
- Messinian seep-carbonates marking the transition to the evaporite
deposits in the Romagna sector of the northern Apennines (Italy)
[Articolo su rivista]
Conti, S.; Fioroni, C.; Serventi, P.; Fontana, D.
abstract
2022
- Petrographic features to formere presence of gas hydrate in ancient seep carbonates: preliminary observations of moderm and fossil material
[Relazione in Atti di Convegno]
Giunti, S.; Bohrmann, G.; Conti, S.; Dela Pierre, F.; Fontana, D.; Martire, L.; Natalicchio, M.; Wetzel, A.; Bojanowski, M.
abstract
2021
- Biomarker constraints on Mediterranean climate and ecosystem transitions during the Early-Middle Miocene
[Articolo su rivista]
Salocchi, Aura C.; Krawielicki, Julia; Eglinton, Timothy I.; Fioroni, Chiara; Fontana, Daniela; Conti, Stefano; Picotti, Vincenzo
abstract
2021
- Gas Hydrate destabilization and sea-level changes: insights from Miocene seep carbonate deposits of the northern Apennines (Italy).
[Relazione in Atti di Convegno]
Fontana, D.; Conti, S.; Fioroni, C.; Argentino, C.
abstract
2021
- Miocene Seep-Carbonates of the Northern Apennines (Emilia to Umbria, Italy): An Overview.
[Articolo su rivista]
Conti, S; Argentino, C; Fioroni, C; Salocchi, Ac; Fontana, D
abstract
2021
- Trace fossils in seep-impacted sediments as a tool to decipher the origin
of fine-grained intervals of the Marnoso-arenacea turbidite succession
(Miocene, northern Apennines, Italy)
[Articolo su rivista]
Conti, S.; Baucon, A.; Serventi, P.; Argentino, C.; Fontana, D.
abstract
The Marnoso-arenacea turbidite succession outcropping in northern Italy is one of the most studied deep-water
systems worldwide due to its excellent exposure. Despite the well-established sedimentology of the arenaceous
succession, the origin of fine-grained intervals within the Marnoso-arenacea Fm is reconsidered in the light of
methane-rich fluid expulsion, in particular as seep-carbonates are present. Fine-grained intervals are marked
by limited vertical and lateral extent, in the order of 102 m and 103 m respectively, and are often associated
with small-scale sediment deformation. In this study, we conduct a detailed sedimentological and stratigraphic
investigation of the well-exposed Prati Piani fine-grained interval (Serravallian in age) with particular focus on
the characterization of trace fossils and seep-carbonates. Trace fossils interpreted as Thalassinoides are widespread
throughout the interval and form a complex network testifying long-lasting burrowing activity of decapod
crustaceans. Seep-carbonates crop out at different stratigraphic levels and form meter-sized blocks with
δ13C from−33.2‰ to−18.2‰. The occurrence of aragonite cements and fossil chemosymbiotic fauna indicates
episodic carbonate precipitation close to the paleo-seafloor. Although crustaceans have been frequently reported
grazing microbial mats atmodern seeps and leaving a 13C-depleted isotopic signature in trace fossils, in our study
we found only one slightly depleted δ13C value (−9.5‰,) allowing us to exclude preferential authigenesis. Moreover,
burrows are filled by detrital fine-grained sediments and hemipelagic micrite that may have diluted the
methane-related signature. The association between in situ seep-carbonates and well-preserved trace fossils is
of use to interpret the interval as formed by fine-grained sedimentation draping a thrust-related anticline. In
this model, the stratigraphically- and laterally-confined deformed zones affecting the Prati Piani interval reflect
in-situ soft-sediment deformation and small-scale slumping induced by fluid seepage along the ridge, consistent
with present-day observations from several continental margins worldwide.
© 2021
2021
- Trunk river and tributary interactions recorded in the Pleistocene–Holocene stratigraphy of the Po Plain (northern Italy)
[Articolo su rivista]
Bruno, L.; Amorosi, A.; Lugli, S.; Sammartino, I.; Fontana, D.
abstract
Tributary rivers can contribute significantly to alluvial-plain construction by supplying large volumes of clastic material. Their relation to the main axial river strongly influences sediment deposition and preservation. The Po Plain is fed by the Po River and a dense network of transverse tributaries draining the nearby Alpine and Apennine chains. Stratigraphic, sedimentological, petrographic and geochemical analyses on 38 cores permitted detailed differentiation of Po and Apennine sedimentary units. Po River deposits are vertically stacked channel-belt sand bodies with high contents of quartz–feldspar and metamorphic rock fragments, combined with high chromium levels. These sand bodies, 20 to 30 km wide, are replaced southward by finer-grained deposits that represent the distal Apennine tributary-rivers system. Apennine sands, confined in narrow ribbons, show lower quartz–feldspar contents, abundant sedimentary lithics and lower chromium levels. In the last 870 kyr, the boundary between the Po and the Apennine sediment delivery systems shifted along a north–south axis in response to distinct controlling factors. A 20 km northward shift of the Po channel belt, possibly related to a tectonic event, is recorded across a regional unconformity dating to the Marine Isotope Stage 12/11 transition. High sediment supply rates during glacial-lowstand periods widened the Po channel belt southward towards the Apennine domain for a few kilometres. The Last Glacial Maximum channel-belt sand body, 30 km wide and 40 m thick, progressively narrowed northward after the glacial culmination. During the Holocene, channel patterns became avulsive and distributive. Narrow channel belts (<3 km) formed along the Po River branches, and abundant swamp and poorly drained-floodplain muds were preserved in interfluvial areas. Activation and deactivation of the Po branches resulted in sharp narrowing and widening of the area available for Apennine-rivers sedimentation. This work provides insights into tributary-trunk river relations which control grain-size distribution and compositional characters of subsurface deposits.
2020
- Blast-induced liquefaction in silty sands for full-scale testing of ground improvement methods: Insights from a multidisciplinary study
[Articolo su rivista]
Amoroso, S.; Rollins, K. M.; Andersen, P.; Gottardi, G.; Tonni, L.; Garcia Martinez, M. F.; Wissmann, K.; Minarelli, L.; Comina, C.; Fontana, D.; De Martini, P. M.; Monaco, P.; Pesci, A.; Sapia, V.; Vassallo, M.; Anzidei, M.; Carpena, A.; Cinti, F.; Civico, R.; Coco, I.; Conforti, D.; Doumaz, F.; Giannattasio, F.; Di Giulio, G.; Foti, S.; Loddo, F.; Lugli, S.; Manuel, M. R.; Marchetti, D.; Mariotti, M.; Materni, V.; Metcalfe, B.; Milana, G.; Pantosti, D.; Pesce, A.; Salocchi, A. C.; Smedile, A.; Stefani, M.; Tarabusi, G.; Teza, G.
abstract
In the engineering geology field increased attention has been posed in recent years to potential liquefaction mitigation interventions in susceptible sand formations. In silty sands this is a major challenge because, as the fines content increases, vibratory methods for densification become progressively less effective. An alternative mitigation technique can be the installation of Rammed Aggregate Pier® (RAP) columns that can increase the resistance of the soil, accounting for its lateral stress increase and for the stiffness increase from soil and RAP composite response. To investigate the influence of these factors on liquefaction resistance, full-scale blast tests were performed at a silty sand site in Bondeno (Ferrara, Italy) where liquefaction was observed after the 2012 Emilia-Romagna earthquake. A multidisciplinary team of forty researchers carried out devoted experimental activities aimed at better understanding the liquefaction process at the field scale and the effectiveness of the treatment using inter-related methods. Both natural and improved areas were investigated by in-situ tests and later subjected to controlled blasting. The blast tests were monitored with geotechnical and geophysical instrumentation, topographical surveying and geological analyses on the sand boils. Results showed the RAP effectiveness due to the improvement of soil properties within the liquefiable layer and a consequent reduction of the blast-induced liquefaction settlements, likely due to soil densification and increased lateral stress. The applied multidisciplinary approach adopted for the study allowed better understanding of the mechanism involved in the liquefaction mitigation intervention and provided a better overall evaluation of mitigation effectiveness.
2020
- Development and Use of a Minicone for Liquefaction Risk Evaluation in Layered Soil Deposits
[Articolo su rivista]
Meisina, C.; Öztürk Kardoğan, P. S.; Bonì, R.; Stacul, S.; Castaldini, D.; Fontana, D.; Lugli, S.; Bordoni, M.; Lo Presti, D.
abstract
This paper shows and compares the experimental results obtained by using a standard cone (10 cm2) and a mini piezocone
(2 cm2). Tests were carried out at Calendasco (Piacenza, Italy) in a natural soil deposit mainly consisting of clayey-sandy silts. Grain size
distribution with depth was also available. Other tests were carried out at Cavezzo (Modena, Italy), where liquefaction-induced phenomena
were observed during the May 29, 2012, seismic sequence. The purpose was to investigate capabilities and limitations of mini piezocone and
to explore the possibility of obtaining a better prediction of soil stratigraphy in thin layered deposits. Systematic differences in terms of tip
resistance and sleeve friction were not observed, even though, generally, qc standard
2020
- Liquefaction source layer for sand blows induced by the 2016 megathrust earthquake (Mw 7.8) in Ecuador (Boca de Briceño)
[Articolo su rivista]
Salocchi, Aura C.; Minarelli, Luca; Lugli, Stefano; Amoroso, Sara; Rollins, Kyle M.; Fontana, Daniela
abstract
Numerous sand boils were generated in the alluvial plain at the mouth of the Rio Brice˜no valley (Ecuador) during
the Mw 7.8 earthquake of April 2016. The area is characterized by a series of raised marine terraces formed as a
consequence of the rapid tectonic coastal uplift during the Quaternary. Boreholes and geotechnical investigations
were carried during post-earthquake surveys and for the purpose of mitigating the liquefaction effects. Five
lithological units were identified at a site of embankment, which represented continental-marine and transitional
sedimentation since the Last Glacial Maximum. A comprehensive study of texture and petrographic composition
of sand boils has been performed and compared with sandy silts and silty sands of the buried sedimentary
sequence in order to identify the source levels for liquefaction. The petrographic components, in particular the
low content of bioclasts and carbonate fragments of the sand boils, allow to pinpoint a source layer made up of
fine-grained silty sands located between 2 and 4.5 m depth (Unit 2) whereas the deeper marine sands, richer in
bioclasts, were not involved. The results support the idea that earthquake-induced liquefaction phenomena are
not restricted to clean sands and well-sorted deposits, but may affect sand layers with significant amount of nonplastic
silt.
2020
- Preservation of 34S-enriched sulfides in fossil sulfate-methane transition zones: new evidence from Miocene outcrops of the northern Apennines (Italy)
[Articolo su rivista]
Argentino, C.; Johnson, J. E.; Conti, S.; Fioroni, C.; Fontana, D.
abstract
We provide new evidence of the preservation of 34S-enriched signals in methane seep-impacted sediments from two onshore Miocene outcrops located in the northern Apennines (Italy). Selected outcrops include methane-derived authigenic carbonates (MDAC) with δ13C composition between − 42.3 and − 18.2‰. MDACs contain chemosynthetic clams and abundant pyrite indicative of formation close to or within a shallow sulfate-methane transition zone (SMTZ). This study aims to evaluate the relative contributions of background organic matter mineralization and anaerobic oxidation of methane (AOM) to sulfate consumption and to gain insight into the transport process (i.e., diffusion, advection) controlling the depth of the SMTZ. Host sediments were investigated by CHN elemental analysis coupled with total sulfur (TS) and sulfur isotopic measurements on bulk samples. Total organic carbon (TOC) measurements reveal a consistent and low amount of organic carbon (TOC< 0.5%), with no notable difference between the underlying turbidites and the stratigraphic intervals hosting the MDACs. The TS/TOC ratio of most samples is well above the baseline value of deposition under normal marine conditions, suggesting the excess TS here is due to enhanced sulfate reduction. The samples show bulk δ34S values commonly enriched (> 0‰ and up to + 17.1‰), which is characteristic of sulfides precipitated in association with AOM. We propose that advection of methane-rich fluids was responsible for maintaining the shallow depth of the studied paleo-SMTZs. AOM at paleo-SMTZ positions in the investigated seep-impacted sediments resulted in excess bicarbonate and sulfide production, favoring solid-phase MDAC and iron sulfide precipitation.
2019
- 3D Geological model reconstruction for liquefaction hazard assessment in the Po Plain
[Relazione in Atti di Convegno]
Meisina, C.; Bonì, R.; Bordoni, M.; Lai, C.; Famà, A.; Bozzoni, F.; Cosentini, R. M.; Castaldini, D.; Fontana, D.; Lugli, S.; Ghinoi, A.; Martelli, L.; Severi, P.
abstract
Liquefaction represents one of the most dramatic effects that may occur during an earthquake. Several controlling factors may influence liquefaction occurrence, such as the earthquake magnitude, the peak ground acceleration, the depth of the groundwater table and the geological context. In particular, the thickness of the potentially liquefiable layers, the grain size of the sediments, the compaction degree and the interaction between different lay-ers may strongly influence the phenomena. Hence, a deep understanding of the liquefying de-posits is fundamental for the hazard assessment. During the Emilia (Northern Italy) earth-quake sequence of May-June 2012 , several liquefaction manifestations were observed. In this work, a 3D geological model for liquefaction hazard assessment is presented for the Cavezzo municipality, which was affected by liquefaction phenomena. The study was performed in the framework of the European project Horizon 2020 "LIQUEFACT” using an interdisciplinary methodological approach involving geologists, geomorphologists, sedimentologists, engineer-ing geologists and geotechnical engineers.
2019
- A deep fluid source of radiogenic Sr and highly dynamic seepage conditions recorded in Miocene seep carbonates of the northern Apennines (Italy)
[Articolo su rivista]
Argentino, C.; Lugli, F.; Cipriani, A.; Conti, S.; Fontana, D.
abstract
The 87Sr/86Sr, REE and MoU systematics were investigated in Miocene seep carbonates formed on accretionary ridges at the front of the northern Apennine wedge. Here we evaluate fluid sources, seepage intensity and redox conditions during carbonate precipitation. Micrite matrix and early calcite cements lining cavities are the main authigenic carbonate phases and show negligible diagenetic alteration. Their AOM-related (anaerobic oxidation of methane) origin is evident from δ13C values ranging from −38.7‰ to −25.7‰. The 87Sr/86Sr ratios in carbonates vary between 0.708659 and 0.709132. Most micrite values fall within the range of Middle Miocene seawater (Langhian, MNN5a biozone), in agreement with the biostratigraphy of the host sediments, thus reflecting precipitation of seep carbonates close to the seafloor. Highly radiogenic 87Sr/86Sr ratios, of early calcite cements and micrite from conduit-rich facies at the base of carbonate bodies, likely derived from the interaction of fluids with detrital clays during the fault-controlled upward migration through the underlying terrigenous turbidite successions. Strong Mo and U enrichments in carbonates, with MoEF and UEF up to 233.5 and 86.6 respectively, coupled with (Mo/U)EF ratios ranging between 0.7 and 9.7, indicate dynamic redox conditions, episodically sulfidic and restricted to porewaters. This interpretation is also supported by enrichments in MREE of micrites and a general absence of negative Ce anomalies. These new data provide an indirect indication of rates and temporal variability of AOM at fossil methane seeps developed on a thrust related anticline and help to constrain the complex interaction between fluid migration pathways, seepage intensity and environmental conditions as observed in modern seep analogues.
2019
- Biostratigraphic distribution of Miocene carbonates associated with gas hydrates in the northern Apennines (Italy) and their relationship with sea-level lowering
[Abstract in Atti di Convegno]
Fioroni, Chiara; Argentino, Claudio; Conti, Stefano; Fontana, Daniela
abstract
Gas hydrates are widespread in modern continental margins and their stability is related to temperature, pressure and availability of gas and water. Their sensitivity to tectonic activity and climate is still poorly constrained and more efforts are needed to understand how they respond to these forcing processes. Gas hydrates are frequently associated with carbonates, called clathrites, that may form bodies of large dimension and are marked by geochemical indicators such as 13C-depleted and enriched 18O values.
A number of Miocene seep-carbonates outcrop in different geological settings of the northern Apennines (Italy) (Argentino et al., 2019a), showing characters suggesting paleo-gas hydrate occurrence and then can be considered as clathrites. Our biostratigraphic investigation on the sediment enclosing gas-hydrate associated carbonates has shown that they are roughly concentrated in three main intervals: in the Langhian (subzone MNN5a), in the upper Serravallian-lower Tortonian (subzone MNN6b to zone MNN7) and the upper Tortonian-lowermost Messinian (zones MNN10 and MNN11). By comparing seep distributions with 3rd order eustatic curves of Haq et al. (1987), they seem to match phases of sea-level lowering.
The relationship among gas hydrate destabilization, climate change, sea-level variations, tectonic activity and fluid circulation, is particularly challenging in the fossil record. In the examined carbonates, a drop in the hydraulic pressure on the plumbing system during sea-level lowering would have shifted the base of the gas hydrate stability zone into shallower depths, inducing gas-hydrate destabilization. The uplift of the different sectors of the wedge-top foredeep system during tectonic migration could have increased the effect of the concomitant eustatic sea-level drop, reducing the hydrostatic load on the seafloor and inducing gas-hydrate decomposition.
In this view, a precise biostratigraphic framework of paleo-clathrites in the sedimentary record may help to shed light into gas-hydrates long-term evolution and their relation with sea level changes and tectonics.
2019
- Evidences for Paleo-Gas Hydrate Occurrence: What We Can Infer for the Miocene of the Northern Apennines (Italy)
[Articolo su rivista]
Argentino, C.; Conti, S.; Fioroni, C.; Fontana, D.
abstract
The occurrence of seep-carbonates associated with shallow gas hydrates is increasingly
documented in modern continental margins but in fossil sediments the recognition of gas hydrates
is still challenging for the lack of unequivocal proxies. Here, we combined multiple field and
geochemical indicators for paleo-gas hydrate occurrence based on present-day analogues to
investigate fossil seeps located in the northern Apennines. We recognized clathrite-like structures such
as thin-layered, spongy and vuggy textures and microbreccias. Non-gravitational cementation fabrics
and pinch-out terminations in cavities within the seep-carbonate deposits are ascribed to irregularly
oriented dissociation of gas hydrates. Additional evidences for paleo-gas hydrates are provided by
the large dimensions of seep-carbonate masses and by the association with sedimentary instability
in the host sediments. We report heavy oxygen isotopic values in the examined seep-carbonates up
to +6h that are indicative of a contribution of isotopically heavier fluids released by gas hydrate
decomposition. The calculation of the stability field of methane hydrates for the northern Apennine
wedge-foredeep system during the Miocene indicated the potential occurrence of shallow gas
hydrates in the upper few tens of meters of sedimentary column.
2019
- Fluid expulsion in accretionary wedges: what can we learn from
Miocene seep carbonates (Emilia and Tuscan Apennines, Italy)
[Capitolo/Saggio]
Fontana, D.; Conti, S.; Argentino, C.; Fioroni, C.
abstract
Seepage of hydrocarbon-rich fluids is a common process
in accre onary wedges where tectonic thickening and
underpla ng generate pore-fluid overpressures and
induce fluid migra on (Bohrmann et al., 2002; Gill et al.,
2005; Ding et al., 2010; Crutchley et al., 2015; Klaucke et
al., 2015). The migra on and expulsion of methane-rich
fluids promote the precipita on of a variety of authigenic
minerals on the seafloor or within the sediments, i.e.
carbonates (aragonite, calcite, dolomite), sulfides and
sulphates, forming crusts, concre ons and build-ups.
Reduced compounds in the fluids also sustain peculiar
microbial consor a and macrofaunal communi es
(Teichert et al., 2005; Campbell, 2006) (Fig. 1).
It is widely recognized that the most reliable indicators of
fossil cold seeps are the anomalously nega ve carbon
13 isotope composi on of the carbonates, with d C values as
low as -60‰ VPDB (Judd and Hovland, 2009), the peculiar
chemosynthe c bivalves (Lucinidae and Vesicomyidae)
and specific biomarkers (e.g. Taviani, 2014; Peckmann et
al., 2002; Grillenzoni et al., 2017).
In the northern Apennine orogenic belt, several outcrops
of authigenic carbonates tes fy for Miocene seepage
ac vity (Terzi et al., 1994; Dela Pierre et al., 2010; Con et
al., 2017). These carbonates show highly depleted d13C
signatures and host large chemosynthe c bivalve
assemblages (mainly giant lucinids)(Grillenzoni et al.,
2017), thus tes fying a long and complex history of
methane-rich fluid ven ng on the sea floor. Apenninic
carbonate deposits bearing fossil chemosynthe c fauna
have been found in various domains and basin types, from
wedge-top basins to the slope of the accre onary wedge,
and in the inner foredeep (Con and Fontana, 1999;
Argen no et al., 2019a) (Figs 2, 3).
In the following, we summarize and describe the main
features of the Apennine seep carbonates, from field
observa ons to geochemical features.
2019
- Formation of tubular carbonate conduits at Athina mud volcano, eastern
Mediterranean Sea
[Articolo su rivista]
Tamborrinoa, L.; Himmlerb, T.; Elvert, M.; Conti, S.; Gualtieri, A.; Fontana, D.; Bohrmann, G.
abstract
Tubular carbonate conduits (TCC) represent the termination of fluid plumbing systems in environments of hydrocarbon
seepage and play a relevant role in the discharge of methane from sub-seafloor sediments to the water
column. However, the biogeochemical reactions and biological activities involved in their formation are not fully
understood. To address this, TCC samples were collected with a remotely operated vehicle from the seabed on
the SW flank of the Athina mud volcano in the eastern Mediterranean Sea. Petrographic, mineralogical, stable
carbon and oxygen isotope and lipid biomarker analyses were performed to elucidate the formation processes of
the tubular carbonates. Clotted and fibrous aragonite form the internal lining of the cavities, while the outer
portion of the tubes is formed by micritic Mg-calcite cementing hemipelagic sediment. 13C-depleted Mg-calcite
and aragonite (as low as −14.4‰ V-PDB) and lipid biomarkers (archaeol, −89.8‰ V-PDB) indicate that carbonate
precipitation was influenced by sulfate-dependent anaerobic oxidation of methane (AOM). AOM locally
enhances aragonite precipitation, thereby facilitating early lithification of the conduits within the mud volcano
sediments. The size and morphology of the TCC comparable with the buried portion of tubeworm colonies found
in the proximity of the sampling site. However, our results suggest that TCC likely formed by the action of
burrowing organism rather than being mineralizations of the tubeworm colonies. This study provides new insights
into the interpretation and understanding of TCC, highlighting the role of macrofaunal activity in the
formation of migration pathways for hydrocarbon-rich fluids on the flank of a mud volcano
2019
- Methane-derived authigenic carbonates on accretionary ridges: Miocene case studies in the northern Apennines (Italy) compared with modern submarine counterparts
[Articolo su rivista]
Argentino, C.; Conti, S.; Crutchley, J. C.; Fioroni, C.; Fontana, D.; Johnson, J. E.
abstract
We present new field data from three outcrops of Miocene methane-derived authigenic carbonates in the
foredeep of the northern Apennines that contain chemosynthetic fauna and record a long history (∼1 Ma) of
shallow fluid seepage linked to seafloor anaerobic oxidation of methane. The studied outcrops show similar
features in terms of carbonate morphology, facies, spatial distribution and lateral and vertical contacts with the
enclosing sediments. Methane-derived carbonates occur in two structural positions: 1) on the slope of the accretionary
wedge in hemipelagites draping buried thrust-related anticlines, and 2) at the leading edge of the
deformation front in the inner foredeep, within fault-related anticlines standing above the adjacent deep seafloor
as intrabasinal ridges. We compare fossil seeps with two extensively investigated modern analogues: the
Hikurangi Margin, offshore New Zealand and Hydrate Ridge, on the Cascadia margin, offshore the U.S.A. These
analogues share a similar compressive structural setting and are marked by the presence of variably extensive
and voluminous methane-derived carbonate bodies and chemosynthetic fauna on the present-day seafloor. The
comparison allows us to propose a model for the evolution of fluid seeps on thrust-related ridges. At the deformation
front, uplift and geometry of the anticlinal ridges are controlled by the growth of splay faults, mostly
blind, connected to the basal detachment, favoring the migration of fluids toward the incipient anticline. Fold
development generates extensional stresses in the hinge zone of the anticline, promoting the development of
normal faults; fluid migration pathways and seafloor seeps shift from the forelimb toward the crest of the ridge
as the structures evolve. In the slope setting, far from the deformation front, thrust faults and extensional faults
in buried anticlines remain the main fluid migration pathways to sustain seepage at the seafloor. After reaching a
mature stage within the wedge, the structure is less active and buried in the slope environment of the evolved
2019
- Sand liquefaction induced by a blast test: New insights on source layer and grain-size segregation mechanisms (Late Quaternary, Emilia, Italy)
[Articolo su rivista]
Fontana, Daniela; Amoroso, Sara; Minarelli, Luca; Stefani, Marco
abstract
The composition and texture of liquefied sands represent an important tool for the recognition of buried source layers and for a better understanding of earthquake-induced liquefaction mechanisms. The earthquake-simulating field experiment (blast test) carried out in 2016 in fluvial sediments of the Emilia plain induced subsurface liquefaction and the surface expulsion of sand as sand blows. The area was widely affected by liquefaction phenomena during the Mw 6.1 Emilia earthquake (2012). The grain size and composition of sand blows ejected during the blast test have been compared with various horizons of buried fluvial sediments as deep as 20 m, and with sands from two trenches in the blast site representative of co-seismic 2012 liquefied sands. The sands from the cores show a clear trend from shallow lithoarenitic to deeper quartz–feldspar-rich compositions. The sands at shallow depth (up to 7.7 m) are the most lithoarenitic, with fine-grained sedimentary rock fragments (shales, siltstones, and limestone) as the dominant lithic type. Lithic fragments derive mostly from erosion of sedimentary terrigenous and carbonate successions of Apenninic affinity. In contrast, deeper sands (at depth . 7.7 m) are enriched in quartz and feldspars and impoverished in lithic fragments, which are similar in character to Po River sands. The composition of ejected sands largely overlap that of the shallow litharenitic Apenninic sands, indicating that liquefaction processes affected mainly sand layers at relatively shallow depth (5.9–7.7 m). Textural parameters show that silty sands and silts characterized by relatively high content of fines can also liquefy. This is in contrasts to most of the literature, where fine-grained sediments are considered as incapable of generating the high pore pressures commonly associated with liquefaction. This result should be considered when estimating the liquefaction as a potential hazard. Moreover, we observe that there is a selective loss of fines in the clastic dikes and sand volcanoes relative to the source beds, indicating that the liquefaction process appears to preferentially select the diameters of the grains that reach the ground surface, probably following the generated excess pore-water pressure. This may have caused the segregation and dispersion of the fine silt–clay content, producing highly sorted sand boils. This effect is easily observable in both the blast-induced sand boils, and the co-seismic 2012 dikes and sand boils ejected in the same area.
2019
- Sedimentary structures and textures in sand injectites. Insights from dikes and
sand blows of the Holocene fluvial sediments (Emilia, Italy)
[Abstract in Atti di Convegno]
Fontana, D.; Lugli, S.; Salocchi, A. C.
abstract
As discussed by Hurst et al. (2011), studies of sand injectites, including sand extrusions, are relatively scarce in the geological literature, although these phenomena were recognized in many geological settings (Quigley et al., 2013: Ross et al., 2014).
A trench dug across dikes and sand blows formed as a consequence of the 2012 Emilia earthquake allowed a direct observation of liquefaction structures (Fontana et al., 2015, 2019). Sand dikes crosscut the fine-grained host sequence at high angles with a vertical extension of at least 5 m. The width of the fractures varied from a few cm to 30 cm. The injected sand showed complex sedimentary structures: the most common was a distinct banding, longitudinal to the dike length, or perpendicular to the dike margins. The bands oriented parallel to the dike were bounded by sharp contacts marked by thin clay veneers defined by differences in grain size and grain alignment. We observed both direct and inverse vertical grading from medium sand to mud. The fractures were rhythmically injected and filled of slurry sand and mud during the compression pulses end emptied by the rushing of the slurry back down deep into the fractures during the extension peak.
The grain-size distribution along dikes and sand blows showed that some sorting occurred within injected dikes, probably due to pulse flows, and further segregation occurred as the material was extruded following the generated excess pore-water pressure. This may have caused the dispersion of the fine silt–clay content, producing highly sorted sand boils.
The composition of sand dykes adds an important constraint in identifying the source layer. Regarding the possibility that selective mechanism due to flux variation may have influenced the sand composition, our data seem to indicate that no major variation was induced by injection phenomena.
2018
- Constraining the fluid source of Miocene seep carbonates using radiogenic Sr isotopes (Corella outcrop, northern Apennines, Italy)
[Abstract in Atti di Convegno]
Argentino, Claudio; Lugli, Federico; Cipriani, Anna; Conti, Stefano; Fioroni, Chiara; Fontana, Daniela
abstract
Analisi isotopiche e biostratigrafiche su corpi carbonatici metanoderivati dell'Appennino settentrionale
2018
- High-resolution chemostratigraphy of a Miocene wedge-top carbonate shelf (San Marino Fm., Northern Apennines, Italy): The major role of the Monterey global fertility event
[Articolo su rivista]
Salocchi, Aura Cecilia; Preto, Nereo; Fontana, Daniela
abstract
The evolution of the San Marino carbonate succession, developed on a wedge-top basin of the northern Apennines during the Middle Miocene (Torriana outcrop, Marecchia Valley), was studied through a high-resolution stable isotope analysis on different carbonate components. A marked positive carbon isotopic excursion is identified at ca. 16 Ma. The excellent correlation of the San Marino δ13C carbonates with the global δ13C reference curve from Zachos et al. (2008) allows to link the marked positive δ13C present in the San Marino section with the global carbon isotope maximum of the Monterey event. Subordinate long-eccentricity-driven δ13C cycles (~405 kyr) as recorded by Holbourn et al. (2007) were also identified. The correlation with carbon signatures of coeval successions of the Mediterranean region shows that this main carbon isotopic excursion at the Burdigalian–Langhian boundary is widely recorded and predates the crisis of these heterozoan shelves. The demise of the San Marino shelf resulted from a combination of global and regional factors that controlled the nutrient budget, the detrital input and the subsidence of the basin. The high-resolution chemostratigraphy of San Marino succession shows that even though the shelf evolved in the complex setting of a wedge-top basin, which should be largely influenced by local factors (i.e. tectonic subsidence and detrital input), it records the Monterey event and its eccentricity paced rhythms with high precision. This highlights the strong connection of the Monterey event with the development and subsequent demise of shallow water carbonate depositional systems in the Mediterranean, irrespective of variable and changing local conditions.
2018
- Highly dinamic redox condition and fluid source identification in seep impacted sediments revealed by Mo-U enrichments, 87Sr/86SR and REE pattern (Miocene, Mugello outcrops, northern Apennines)
[Abstract in Atti di Convegno]
Argentino, C.; Lugli, F.; Cipriani, A.; Conti, S.; Fioroni, C.; Fontana, D.
abstract
cold seeps have been increasingly identified.....
2018
- Sand Liquefaction Phenomena During the Seismic Crisis of May 2012 in Emilia, Northern Italy
[Articolo su rivista]
Lugli, Stefano; Fontana, Daniela; Marchetti, Dori Simona; Fioroni, Chiara; Bertolini, Giovanni
abstract
In May 2012, the Emilia region of the Po Valley was struck by a seismic crisis with two major events of magnitude Mw6.1 and Mw5.9. The first event induced widespread sand blows formed along buried channels and old crevasse splay deposits. In the days immediately following the events, the detailed mapping and sampling of the erupted sand was fundamental to record all the seismically-induced phenomena. The study of a trench dug across large fractures at San Carlo (Ferrara) provided also valuable information on the sand blows mechanism and regome. The sedimentological and compositional characteristics of the fracture-filling materials indicate that the sands were erupted from a layer located between 6.8 and 7.5 m depth. Older and deeper Holocene and Pleistocene sand layers were not apparently involved in the liquefaction phenomena.
2018
- Sand composition as a tool for liquefaction phenomena assessment
[Abstract in Atti di Convegno]
Fontana, Daniela; Lugli, Stefano
abstract
The petrographic composition of sands is a useful tool for the assessment of the complex
phenomena related to co‐seismic liquefaction, such as sand blows, dykes, sand volcanoes and
may also help in identifying ancient earthquake effects.
Fluvial sand composition studies have a particular significance in the late Pleistocene–Holocene Po
Plain, where distinct compositional fields characterize modern sands from different streams, as well
as older sediments1
. Several key petrographic components provide diagnostic features to distinguish
sand bodies buried beneath the floodplain.
The composition of sands ejected during the 2012 Mw 6.1 Emilia earthquake from several sites in
the Emilia plain (Modena and Ferrara provinces)2 has been compared with buried sands from cores
and trenches at different depths (down to 50 m) in order to identify the source layers which
originated the liquefaction phenomena.
The sands from the cores show a clear trend from lithoarenitic to quartz‐feldspar‐rich compositions.
The sands at shallow depth (down to 7 m) are the most lithoarenitic, with sedimentary fine‐grained
rock fragments (limestone, shale and siltstone) as the dominant lithic type. Lithic fragments derive
mostly from the erosion of sedimentary terrigenous and carbonate successions of Apenninic affinity
referable to different fluvial systems (Secchia and Reno rivers). These shallow sands are well
distinguishable from the deeper sands (at depth > 7 m), which show compositions slightly enriched
in quartz and feldspars and impoverished in lithic fragments suggesting affinity with the Po river
sands or older sands deposited during the last Glacial Maximum.
In all examined sites the composition of the ejected sands largely overlap that of the shallow late
Holocene Apenninic sands, indicating that liquefaction processes affected mainly sand layers at
depth of 6‐7.5 m.
The study shows that composition of sands is crucial for a better understanding of earthquake‐
induced liquefaction mechanisms, in particular to identify the source layer of the sand blows and,
more generally, for the recognition of critical layers, which may be prone to hazardous sand
liquefaction phenomena.
2017
- Correlating shelf carbonate evolutive phases with fluid expulsion episodes in the foredeep (Miocene, northern Apennines, Italy)
[Articolo su rivista]
Conti, Stefano; Fioroni, Chiara; Fontana, Daniela
abstract
In the Miocene of the northern Apennines of Italy, evolutionary phases of shallow-water carbonates in
wedge-top basins are coeval with methane-rich fluid expulsion episodes in the inner foredeep. We
identified four main correlative events, primarily controlled by synsedimentary tectonics, sediment input
and climate cooling: 1) a Burdigalian tectonic phase determined the onset of shelfal sedimentation in
wedge-top areas and is correlated with an important episode of fluid expulsion in marly sediments of the
inner foredeep (Croce di Moggiona seep-carbonates); 2) the decrease of shelfal carbonate production and
the increase of detrital input in the Early Langhian correspond with a second important episode of seepcarbonate
precipitation in the inner foredeep (Castagno d'Andrea); 3) the demise of the carbonate shelf
and the coeval expulsion of methane-rich fluids in the inner foredeep (Vicchio and M. Citerna seepcarbonates)
at the Langhian/Serravallian boundary approximate the Mi3b cooling event. The lower
temperatures, associated with increased siliciclastic weathering, led to the crisis of shallow-water carbonate
production whereas the pressure drop due to the eustatic fall may have triggered the gas-charged
fluid expulsion; 4) the tectonic-related uplift of frontal sectors of the wedge-top basin led to the wide
erosion of the Burdigalian-Langhian carbonates and caused the precipitation of authigenic seepcarbonates
(Deruta seep) both in the slope and the adjacent foredeep.
2017
- Evolution of a Miocene carbonate shelf (northern Apennines, Italy) revealed through a quantitative compositional study
[Articolo su rivista]
Salocchi, AURA CECILIA; Argentino, Claudio; Fontana, Daniela
abstract
The evolution of the Miocene San Marino carbonate shelf (Torriana outcrop), developed on the accretionary prism of the northern Apennines, has been interpreted through a stratigraphic and compositional study. Modal analysis allowed to quantify the framework components and to identify four microfacies through which the main steps of the carbonate ecosystem were traced. The healthy phase of the carbonate shelf, dominated by bryozoans and echinoids, originated in a high-energy transgressive setting and evolved during a warm period characterized by a progressive increase of nutrients. The transitional stage is marked by a reduction of carbonate productivity and by terrigenous intermittent pulses associated with bioclast fragmentation. The drowning succession corresponds to deepening upward facies formed by fine-grained hybrid arenites to sandy marls with abundant planktonic foraminifera, glauconitic grains and clay matrix. The demise of the carbonate shelf might have resulted from a combination of regional and global factors that interplayed controlling the detrital input, the nutrient budget and the deepening of the basin. Synsedimentary tectonics triggered subsidence of the basin and enhanced terrigenous discharge. Moreover, the superposition of paleoclimatic and paleoceanographic events (Monterey and Middle Miocene Climate Optimum) could have contributed with the intense weathering and remarkable detrital and nutrients supply.
2017
- MIOCENE SEDIMENTARY INSTABILITIES ASSOCIATED WITH
METHANE DERIVED AUTHIGENIC CARBONATES: A NEW CASE
STUDY FROM THE NORTHERN APENNINES (PALAZZUOLO
OUTCROPS, ITALY)
[Abstract in Atti di Convegno]
Argentino, Claudio; Johnson, Joel; Conti, Stefano; Fioroni, Chiara; Fontana, Daniela
abstract
Northern Apennines (Italy) host several outcrops of methane derived seep carbonates often associated
with sedimentary instabilities such as intraformational slumps, extraformational slides and diapiric
processes. Despite the vast body of literature on seep-deposits from the Monferrato to the Umbro-Tuscan
sectors of the mountain chain, only a few studies focus on the interplay between paleomethane seepage and
sedimentary instabilities (Conti and Fontana, 2002) because of the lack of good exposures.
In this study we investigate an outcrop located in the Mugello area of the Tuscan Apennines (Prati
Piani di Palazzuolo) characterized by the co-occurrence of methane derived authigenic carbonates,
chemosynthetic fauna and slump-like structures. The examined outcrop consists of several carbonate blocks
with max length of 3.5 m enclosed in a 100 m thick pelitic interval, interpreted as sedimentation above a
structural high in the inner foredeep at the front of the Middle Miocene accretionary wedge.
The blocks are mainly located at the base of the pelitic interval and have the same strike as the
enclosing sediments. At various levels, pelitic sediments show soft sediment deformation structures (folds,
slumps). Within the slumps, we sampled some concretions (silty-carbonate in composition).
The δ13C value in the carbonates ranges between -18.2‰ and -33.22‰, confirming they are methane
derived (AOM-related in origin). Pelites surrounding the carbonate blocks (in situ or transported for a short
distance. Isotopic δ18O values are comprised between -4.31‰ and 0.87‰. The concretions are slightly
depleted in 13C (-5.47‰; -10.95‰).
Preliminary data suggest the presence of a seepage system active before the onset of the instability
and able to sustain chemosynthetic communities at the seafloor. The interstitial overpressures might have
reduced the shear strength of the fine-grained sediments and constituted an important preconditioning factor
for diapiric or mass-transport structures. However, this conclusion is still speculative and needs further
investigation.
2017
- Miocene seep-impacted sediments and authigenic carbonates of the Mugello area (northern Apennines, Italy): new insights from facies, stable isotopes and CHN analyses
[Poster]
Argentino, Claudio; Johnson, J. E.; Conti, Stefano; Fioroni, Chiara; Fontana, Daniela
abstract
Reconstructing seepage dynamics and geochemical conditions that created massive authigenic carbonate precipitation and sustained chemosynthetic fauna on the seafloor at the studied site during the Langhian period of the Miocene.
2017
- Mud diapirs originated from mud-rich mass transport deposits: exhumed field cases and modern analogues
[Abstract in Atti di Convegno]
Pini, Gian Andrea; Conti, S.; Festa, A.; Fontana, D.; Lucente, C. C.; Ogata, K
abstract
sedimentary instability
2017
- Paleoenvironmental evolution in a high-stressed cold-seep system (Vicchio Marls, Miocene, northern Apennines, Italy)
[Articolo su rivista]
Grillenzoni, Claudia; Monegatti, Paola; Turco, Elena; Conti, Stefano; Fioroni, Chiara; Fontana, Daniela; Salocchi, AURA CECILIA
abstract
Excellent exposures of Miocene seep-carbonates enclosed in marine marly sediments (Vicchio outcrops in the
northern Apennines, Italy) offer the opportunity to highlight the evolution of a fossil seep ecosystem and the
response of benthic communities to high-stressed environmental conditions. For this purpose, seep-related facies
and molluscs within carbonate bodies have been studied, coupled with benthic foraminiferal assemblages and
carbon and oxygen isotopes in the enclosing marls. The integrated planktonic foraminiferal and calcareous
nannofossil biostratigraphy has allowed us to constrain the seepage within well-calibrated bioevents and to
stress the relationships with paleoclimatic and paleoceanographic variations during the middle Miocene in the
Mediterranean area. Our biostratigraphic data indicate that the onset of the seepage approximates the Mi3b
cooling event (13.82 Ma) and the seepage system lasts for 400 kyr. The evolution of the Vicchio cold-seep system
passes through four phases: (1) The onset of the seepage, characterized by a pervasive flow of methane-rich
fluids, is inferred by δ13C depletion of marly sediments and by prevailing benthic foraminifera indicative of
suboxic conditions at the sea-floor. (2) The methane flow becomes focused causing the precipitation of wide
pinnacle-like carbonate bodies which contain giants lucinids. Enclosing marls indicate well-oxygenated conditions,
possibly enhanced by paleoceanographic variations connected to the Mi3b cooling event. (3) The appearance
of the vesicomyid Christineconcha cf. C. regab and the absence of lucinids in seep-carbonates suggest
stable methane-rich fluid emissions; higher flow rates locally favoured the flourishment of bacterial mats.
Benthic foraminifera show abundance peaks of organic matter depending taxa. (4) The reduced intensity of
methane-rich fluid flows favours the precipitation of stratiform carbonate bodies along strike; the macrofauna is
characterized by the presence of both Vesicomyidae and giant lucinids. Foraminiferal assemblages in the enclosing
marls indicate the restoration of well-oxygenated conditions.
2017
- RECONSTRUCTING SEEPAGE DYNAMICS OF A MIOCENE SYSTEM
THROUGH SEDIMENTOLOGICAL AND GEOCHEMICAL
CHARACTERIZATION OF AUTHIGENIC CARBONATES AND HOST
SEDIMENTS (CORELLA, NORTHERN APENNINES, ITALY)
[Abstract in Atti di Convegno]
Argentino, Claudio; Johnson, Joel; Conti, Stefano; Fioroni, Chiara; Fontana, Daniela
abstract
New data from facies, stable isotopes (C and O) and CHN analyses on seep-impacted sediments and
authigenic carbonates provided insights into dynamics and geochemical background conditions at a Miocene
seepage system (Corella outcrops, northern Apennines, Italy).
The examined outcrops comprise 4 lenticular carbonate bodies with maximum length of 200 m and
thickness up to 12 m. These carbonates strike parallel to the bedding of the enclosing sediments and show
lateral pinch out terminations. Chemosynthetic fauna (mainly Lucinids and Vesycomids) are very common
and forms local concentrations of disarticulated or articulated shells; veins and conduits crosscut the
carbonate bodies. Microfacies show mottled micrite including clotted textures related to bacterial activity
and framboids of pyrite (rosette-like features observed at SEM). δ13C values of the carbonates (micrites and
sparry cement filling veins) range between -42.32‰ to -26.63‰ and are indicative of AOM. The δ18O range
between -5.67‰ to 1.13‰ (average -0.96‰) and is close to the Miocene seawater signature and therefore
considered unaffected by significative diagenetic alteration. The host sediments at the top of the carbonates
body is depleted in 13C compared to normal marine carbonates and range between -8.40‰ to -4.75‰ and
δ18O is comprised between -3.50‰ and 1.68‰. CHN analyses on the enclosing sediments revealed low TOC
values in the range 0.21-0.72% with an average of 0.37%, similar to other Miocene foredeep successions of
the northern Apennines. The atomic C/N ratio ranges from 8.93 to 14.05 (avg. 10.84) suggesting minor
admixture of land-derived and marine organic carbon.
We suggest, based on field data, geotectonic setting, and geochemical analysis, that a blind fault,
rooted in the underlyingTertiary turbidites, acted as a pathway for deep methane-rich fluids. Advective fluid
flow resulted in a shallow, near seafloor sulfate-methane transition zone (SMTZ), resulting in the anaerobic
oxidation of methane and the precipitation of massive authigenic carbonate. The presence and preservation
of chemosynthetic fauna throughout the authigenic carbonate body indicates much of the advective fluid
flow breached the seafloor, resulting in methane seepage that helped sustain these chemosynthetic
organisms
2017
- STRONTIUM ISOTOPE STRATIGRAPHY AS A CONTRIBUTION FOR DATING
MIOCENE SHELF CARBONATES (S. MARINO FM., NORTHERN APENNINES)
[Articolo su rivista]
Argentino, Claudio; Reghizzi, Matteo; Conti, Stefano; Fioroni, Chiara; Fontana, Daniela; Salocchi, AURA CECILIA
abstract
This paper provides new data on strontium isotope stratigraphy applied to the Miocene heterozoan
shelfal carbonates of the S. Marino Fm. (Marecchia Valley, northern Apennines). Sr isotopic analyses were
carried out on oyster shells, bryozoans and bulk-rocks from the lower-middle carbonate portion of the section.
In the upper part of the succession that shows evidence of detrital influx, 87Sr/86Sr analyses were performed on
foraminifera tests, separating planktonic and benthic forms. Results were compared with calcareous nannofossil
biostratigraphic data from the same levels, in order to test the reliability of Sr dating in mixed carbonate-siliciclastic
sediments. Mean ages obtained from oysters range between 16.9 Ma and 16.3 Ma. Very similar results are obtained
using bryozoans (16.5 Ma to 16.1 Ma) and bulk-rocks (16.8 Ma to 16.2 Ma). These results allow to better constrain
the age of the massive carbonate shelf, referable to the upper Burdigalian. In the upper carbonate-siliciclastic portion
of the shelf, numerical ages obtained from planktonic and benthic foraminifera are in good agreement with
nannofossil biozones (mean ages respectively around 15.3 Ma and 14.5 Ma) although they display wide confidence
intervals. These wide age uncertainties depend on the slow rate of change of marine 87Sr/86Sr through time that
characterizes the interval between ~15 and ~13.5 Ma.
2017
- Source layer identification of liquefied sands ejected during the blast-induced liquefaction test at Mirabello (Ferrara, Italy) through a quantitative compositional study.
[Abstract in Atti di Convegno]
Fontana, Daniela; Sara, Amoroso; Luca, Minarelli; MARCHETTI DORI, Simona; Marco, Stefani
abstract
It is well known that the occurrence of sand liquefaction phenomena may cause significant modifications of soil geotechnical properties and reduction of load-bearing capacity. Recent experiences (New Zealand, United States) have shown that liquefaction can be induced and monitored with field scale blast tests in order to study the related effects on soil chacacteristics. In this context the composition of sand blows represents an important tool to identify the liquefied layers. This study reports the composition of sands ejected during the blast-induced liquefaction test carried out in May 2016 at Mirabello (Ferrara, Italy). In 2012, the same area was largely affected by liquefaction phenomena during the Mw 6.1 Emilia earthquake. Sand samples analyzed in thin section (34 samples, 300 points for each sample, fraction 0125-0.250 mm) include blast-induced sand blows, sands from 2 cores at different depths in the subsurface (from 2 to 20 m) and sands from 2 trenches in the blast site representative of 2012 liquefied sands. The sands from the cores show a clear trend from lithoarenitic to quartz-feldspar-rich compositions. The sands at shallow depth (up to 7 m) are the most lithoarenitic, with sedimentary fine-grained rock fragments (shales and siltstones) as the dominant lithic type. Lithic fragments derive mostly from the erosion of sedimentary terrigenous and carbonate successions of Apenninic affinity. These shallow sands are well distinguishable from the deeper sands (at depth > 7 m) that show compositions slightly enriched in quartz and feldspars and impoverished in lithic fragments that suggest affinity with the Po river sands. The composition of ejected sands largely overlap that of the shallow Apenninic sands at depth from 6 to 7 m. Similarly the sands from the 2012 dikes show a composition of Apenninic affinity compatible with that of the shallow sands. Results from the blast test fit well with data obtained from the study of the sands ejected in the nearby area of San Carlo during the Mw 6.1 earthquake (Fontana et al., 2015). Also in this case, sand composition and fabric indicate that liquefaction processes affected mainly sand layers at relatively shallow depth ( 6.8-7.5 m). The study shows that composition of sands is crucial for a better understanding of earthquake-induced liquefaction mechanisms, in particular to identify the source layer of the sand blows and, more generally, for the recognition of critical levels prone to hazardous sand liquefaction phenomena.
2017
- The first Italian blast-induced liquefaction test 1 (Mirabello, Emilia-Romagna, Italy): description of the experiment and preliminary results
[Articolo su rivista]
Amoroso, Sara; Milana, Giuliano; Rollins, KYLE M; Comina, Cesare; Minarelli, Luca; Manuel, MARIA R; Monaco, Paola; Franceschini, Marco; Anzidei, Marco; Lusvardi, Cameron; Cantore, Luciana; Carpena, Andrea; Casadei, Stefano; Cinti, FRANCESCA R; Civico, Riccardo; Cox, BRADY R; DE MARTINI, PAOLO MARCO; DI GIULIO, Giuseppe; DI NACCIO, Deborah; DI STEFANO, Giuseppe; Facciorusso, Johann; Famiani, Daniela; Fiorelli, Federico; Fontana, Daniela; Foti, Sebastiano; Madiai, Claudia; Marangoni, Valeria; Marchetti, Diego; Marchetti, SILVANO L; Martelli, Luca; Mariotti, Mauro; Muscolino, Elena; Pancaldi, Davide; Pantosti, Daniela; Passeri, Federico; Pesci, Arianna; Romeo, Giovanni; Sapia, Vincenzo; Smedile, Alessandra; Stefani, Marco; Tarabusi, Gabriele; Teza, Giordano; Vassallo, Maurizio1; Villani, Fabio
abstract
Soil liquefaction can result in significant settlement and reduction of load-bearing capacity. Moreover, the increase and the accumulation of pore pressure during an earthquake and its post-seismic dissipation can generate permanent deformations and settlements. The quantitative evaluation of post-liquefaction settlements is of extreme importance for engineering purposes, i.e. for earthquake-resistant design of new buildings and safety evaluation of existing ones. Quantifying the extent of these phenomena is, however, rather difficult. Uncertainties arise from the stochastic nature of the earthquake loading, from the simplifications of soil models, and from the difficulty in establishing correlations between the pre earthquake soil state and the post-seismic deformations. Field scale liquefaction tests, under controlled conditions, are therefore important for a correct quantification of these phenomena. Recent experiences (e.g. New Zealand, United States) show that liquefaction can be induced and monitored with field scale blast tests to study the related effects on soil geotechnical properties. Within this framework this paper introduces the preliminary results obtained from a research project on blast-induced liquefaction at the field scale; tests were performed at a trial site located in Mirabello (Ferrara, Italy), a village strongly affected by liquefaction phenomena during the 2012 Emilia Romagna earthquake. Invasive tests, such as piezocone, seismic dilatometer and down-hole tests, and non-invasive tests were carried out before and after the execution of two blast test sequences to study the variation in physical properties of the soils. Pore pressure transducers, settlement profilometers, accelerometers and an instrumented micropile were installed with the objective of measuring, during and after the detonations, the generation and subsequent dissipation of the pore pressure, the vertical deformations, and the blast-induced ground motions respectively. Variations in load distribution on deep foundations due to soil liquefaction were also evaluated on a test micropile instrumented with a strain gauge chain. Topographical surveys were carried out to measure ground surface settlements. Laboratory tests and trenches also provided increase understanding of the site characteristics.
2017
- The petrography of sands ejected during the blast-induced liquefaction test
(Mirabello, Ferrara, Italy) as a tool to identify the provenance of the source level
[Abstract in Atti di Convegno]
Fontana, Daniela; Amoroso, Sara; MARCHETTI DORI, Simona; Minarelli, Luca; Stefani, Marco
abstract
It is well known that the occurrence of sand liquefaction phenomena may cause significant modifications of soil geotechnical properties and reduction of load-bearing capacity. Recent experiences (New Zealand, United States) have shown that liquefaction can be induced and monitored with field scale blast tests to study the related effects on soil chacacteristics. In this context the composition of sand blows represents an important tool to identify the liquefied layers. This study reports the composition of sands ejected during the blast-induced liquefaction test carried out in May 2016 at Mirabello (Ferrara, Italy). In 2012 the same area was largely affected by liquefaction phenomena during the Mw 6.1 Emilia earthquake. Sand samples analyzed in thin section (34 samples, 300 points for each sample, fraction 0125-0.250 mm) include blast-induced sand blows, sands from 2 cores at different depths in the subsurface (from 2 to 20 m) and sands from 2 trenches in the blast site representative of 2012 liquefied sands. The sands from the cores show a clear trend from lithoarenitic to quartz-feldspar-rich compositions. The sands at shallow depth (up to 7 m) are the most lithoarenitic, with sedimentary fine-grained rock fragments (shales and siltstones) as the dominant lithic type. Lithic fragments derive mostly from the erosion of sedimentary terrigenous and carbonate successions of Apenninic affinity. These shallow sands are well distinguishable from the deeper sands (at depth > 7 m) that show composition slightly enriched in quartz and feldspars and impoverished in lithic fragments. A similar composition suggests affinity with the Po river sands. The composition of ejected sands largely overlap that of the shallow Apenninic sands at depth from 6 to 7 m. Similarly the sands from the 2012 dikes show a composition of Apenninic affinity compatible with that of the shallow sands. Results from the blast test fit well with data obtained from the study of the sands ejected in the nearby area of San Carlo during the Mw 6.1 earthquake (Fontana et al., 2015). Also in this case, sand composition and fabric indicate that liquefaction processes affected mainly sand layers at relatively shallow depth (at depth of 6.8-7.5 m). The study shows that composition of sands is crucial for a better understanding of earthquake-induced liquefaction mechanisms, in particular to identify the source layer of the sand blows and, more generally, for the recognition of critical levels prone to hazardous sand liquefaction phenomena.
2016
- Authigenic carbonates as tracers of methane-rich fluid emission into the sea floor: fossil examples (Miocene, northern Apennines, Italy) compared to modern analogues
[Abstract in Atti di Convegno]
Argentino, Claudio; Conti, Stefano; Fontana, Daniela; Grillenzoni, Claudia; Mecozzi, Silvia
abstract
Cold seepage is a worldwide widespread process recognized in different marine settings of both active and passive continental margins. Authigenic carbonates, deriving from anaerobic oxidation of methane, can be used as tracers for ancient hydrocarbon-rich fluid emissions. Seep-carbonates of the northern Apennines mainly formed during the Miocene, commonly located in the inner part of the foredeep, at the deformation front of the accretionary prism. They are concentrated in two different depositional settings: - in pelitic intervals included in Langhian-Serravallian basin-plain turbidites; - in slope hemipelagites (Burdigalian to Messinian) capping turbidites in proximity to the deformational fronts. Although many of these bodies have been studied yet, significant outcrops still have to be investigated. This study will focus on seep carbonates in the Tuscan-Romagna Apennines (Moggiona). Carbonate bodies have lenticular to stratiform morphologies extending along strike and concordant with the attitude of the enclosing marls. Dimensions vary from 10 to 40 m wide and from 3 to 8 m thick. Carbonates are very rich in lucinid-like clams; at the base, numerous conduits filled with coquina debris and breccias are present, as well as dense irregular networks of carbonate-filled veins and extensional fractures. Carbonates are depleted in δ13C ranging from -40.22 to -19.28‰ V-PDB. The comparison between fossil and modern methane-derived carbonates may allow a better definition of the evolution of the seepage system, and relationships with synsedimentary instability (intraformational slumps and extraformational slides) and diapiric processes
2016
- Depositional history of the Epiligurian wedge-top basin in the Val Marecchia area
(northern Apennines, Italy): a revision of the Burdigalian-Tortonian succession
[Articolo su rivista]
Conti, Stefano; Fioroni, Chiara; Fontana, Daniela; Grillenzoni, Claudia
abstract
The Burdigalian-Tortonian Epiligurian succession in the Val Marecchia area comprehends different
lithostratigraphic units deposited in a wedge-top basin during the northeastern migration of the
thrust belt. The succession includes shallow-water carbonates passing to mixed carbonatesiliciclastic
and to fine-grained pelitic sediments, capped by fluvio-deltaic coarse-grained deposits.
Detailed field work and stratigraphy has allowed to characterize depositional units and
unconformities and to delineate the sedimentary and tectonic evolution of the basin. Tectonics
exerted a primary control at different stages. During the Burdigalian, a general uplift of the area
allowed the onset of shelfal carbonate sedimentation on underlying Ligurian and Epiligurian deepwater
sediments. At the Serravallian the sedimentation was influenced by the thrust reactivations
which caused a marked asymmetry in the basin geometry and fill. The subsidence increase in the
rear part of the basin determined the deposition of a thick succession of relatively deep fine-grained
sediments (up to 800 m water-depth) (Serravallian, MNN6a through MNN6b subzones based on
nannofossil biostratigraphy) and fossiliferous clays (lower Tortonian, biozones MNN8b-MNN9).
Conversely, uplift is activated in the frontal part of the basin, causing the partial erosion of the
Burdigalian–Langhian shallow-water carbonates. A relevant amount of this carbonate detritus is
delivered to the foredeep, supplying the Marnoso-arenacea Fm. A general uplift of the area in the
late Tortonian leads to the deposition of fluvio-deltaic conglomerates supplied by emerged rear
sectors of the basin.
2015
- A quantitative compositional approach to the study of a Miocene carbonate shelf in
the northern Apennines
[Abstract in Atti di Convegno]
Argentino, Claudio; Salocchi, AURA CECILIA; Fontana, Daniela; Grillenzoni, Claudia
abstract
The petrography of 147 samples of carbonate and mixed siliciclastic-carbonate rocks has been
performed on shallow-water carbonates of early-middle Miocene deposited in a wedge-top basin
in the northern Apennines. High-frequency sampling of the Torriana log (Val Marecchia valley,
Romagna Apennines) covers the entire carbonate succession from the basal unconformity to the
terrigenous-rich sediments that mark the demise of the shelf. The modal analysis has been
performed by point counting (300 points) in order to quantify the main framework components:
an intrabasinal carbonate fraction (biogenic), a terrigenous fraction (largely siliciclastic), and an
authigenic intrabasinal component constitued by glauconitic grains.
On the basis of the relative amounts of these framework components, four different petrofacies
are distinguished and matched with lithofacies units. From the base to the top they are the
following:
- Rudstones and subordinate grainstones, made up almost exclusively of intrabasinal carbonate
grains, represented by bryozoans and subordinate echinoid spines and plates. Cement is
constituted by scarce sparry calcite.
- Rudstones to grainstones, made up almost exclusively of intrabasinal carbonate grains plus
very subordinate amounts of siliciclastic grains (quartz, feldspars). Intrabasinal carbonates
consist of shallow-water bioclasts such as bryozoan fragments, echinoid spines and plates, red
algae and benthic macroforaminifera (Amphisteginae, Gypsinae). Grains are cemented by sparry
calcite. Siliciclastic grains are concentrated in thin laminae; isorientation is also occasionally
observable in bioclastic grains (Amphisteginae).
- Hybrid arenites: the intrabasinal carbonate component (biogenic) is associated with variable
but subordinate amounts of terrigenous siliciclastic components dominated by quartz and
feldspar grains (both plagioclase and k-feldspar). The biogenic component is still represented by
bryozoans and echinoids but the bryozoan/echinoid ratio noticeably decreases. The siliciclastic
component is mainly concentrated in thin laminae. The interstitial fraction includes pore-filling
sparry calcite and micritic matrix.
- Arenites, from medium to fine-grained; the terrigenous input noticeably increases and
becomes dominant. It is made up of prevalent quartz and feldspars and few lithics (sedimentary,
metamorphic and volcanic). Intrabasinal grains are subordinate, made up of fragments of algae,
bryozoans, and planktonic foraminifera. Glauconitic grains are present (up to 7% of the whole
rocks); calcite is the dominant pore-filling cement.
The hierarchical cluster analysis of point counting data is in agreement with outcrop-scale facies
observations. Our data indicate an almost exclusively intrabasinal supply during deposition of
the basal portions. A vertical evolution is documented and it is evidenced by a progressive
increase in the terrigenous supply that replaces the bioclastic fraction. The terrigenous input
becomes significant in the upper unit marking the crisis of the shelf.
Abstract
2015
- Caratteristiche sedimentologiche dei depositi di ventaglio di rotta prodotti dal Fiume Secchia durante l’alluvione del 19 gennaio 2014
[Articolo su rivista]
Bigi, D.; Lugli, Stefano; Fontana, Daniela
abstract
Lo studio sedimentologico dei depositi di ventaglio di rotta dell’alluvione del 19 gennaio 2014 presso
San Matteo (Modena) ha permesso di ottenere informazioni sull’evoluzione nel tempo e nello spazio
del sedimento fuoriuscito dall’alveo del Fiume Secchia in soli tre giorni. L’onda di piena ha allagato
la pianura verso nord-est creando un breve solco di erosione e un ventaglio di sabbie dallo spessore
massimo di circa 1 m. Il corpo sabbioso si è sviluppato fino ad una distanza dalla breccia di circa
600 m verso nord-est e 1,1 km verso est, dove la velocità della corrente si è mantenuta superiore
a 0,75 m/s. Nelle zone distali sono stati deposti limi argillosi (16-44% di argilla) fino a 5,4 km di
distanza presso Bastiglia, corrispondenti a velocità della corrente comprese tra 0,75 e 0,25 m/s. Le
sezioni stratigrafiche del corpo sabbioso presentano tre unità principali discontinue, dal basso verso
l’alto: 1) sabbia limosa poggiante direttamente sul terreno agricolo, fuoriuscita nella fase iniziale
dell’alluvione; 2) sabbie medie in discordanza erosiva contenenti abbondanti clasti di fango (16%)
costituiti da frammenti del terreno agricolo e dell’argine stesso prodotti dal progressivo allargamento
della breccia nell’argine; 3) sabbia media con una minore quantità di clasti fangosi (8%)
deposta all’inizio dei lavori di riparazione dell’argine.
Abstract
Sedimentological characteristics of the crevasse-splay deposits of the River Secchia flood of 19th
January 2014. The study of the R. Secchia flood of 19th January 2014 at San Matteo (Modena, Italy)
allows the evolution in time and space of the crevasse-splay deposits, which formed in just three days,
to be reconstructed. The flood propagated toward the north-east forming a small erosion surface
immediately downstream of the collapsed embankment and an irregular sand wedge with a maximum
thickness of about 1 m. The sand body covered an area of about 600 m toward the north-east and 1.1
km to the east, where the speed of the current was higher than 0.75 m/s. Laterally, a thin clayey silt
(16 to 44% of clay) layer was deposited up to 5.4 km away, in the area where the current speed
ranged between 0.75 and 0.25 m/s. The stratigraphic sections of the sand body show three main units,
from the bottom to the top: 1) a layer of silty sand resting directly above the soil, deposited during
the initial phase of the flood; 2) a medium sand layer containing abundant mud clasts (16%) which
are eroded fragments from the soil and the embankment produced by the progressive enlargement of
the breach; 3) a top sand layer with less abundant mud clasts (8%) deposited at the beginning of the
embankment repair works.
2015
- Factors controlling the evolution of a wedge-top temperate-type carbonate platform in the Miocene of the northern Apennines (Italy)
[Articolo su rivista]
Fontana, Daniela; Conti, Stefano; Fioroni, Chiara; Grillenzoni, Claudia
abstract
An integrated study including stratigraphy, composition and biostratigraphy was performed on temperate-type shallow-water carbonates of early middle Miocene age deposited in a wedge-top basin within the Apenninic chain (Romagna-Tuscan area). The succession rests unconformably on the deep-water sediments of allochthonous Ligurian units and is represented by up to 350 m thick carbonates and mixed siliciclastic-carbonate rocks. Two main units are recognized, each characterized by a distinct facies association. The basal unit (upper Burdigalian) consists of rhodalgal rudstones and packstones of shelf environment, dominated by echinoids, bryozoans, coralline algae and benthic foraminifera, deposited in temperate conditions and showing a transgressive pattern. It gradually passes into mixed carbonate-siliciclastic shallow water-facies, (Langhian in age) characterized by an increase in terrigenous components and planktonic and benthic taxa. Sediment starvation during the Langhian is suggested by the occurrence of glaucony-rich packstones with abundant planktonic foraminifera. The succession grades upwards into upper Langhian-lower Serravallian planktonic foraminifera-rich marls. Increasing detrital discharge and water depth up section result in drowning of the carbonate shelf. Debris-flow deposits including material of extraformational origin are intercalated at different levels, in particular from the uplifting south-western margins, close to the Ligurian thrusts. The inception and demise of these temperate rhodalgal-foramol carbonate sediments located in a wedge-top Epiligurian basins is primarily controlled by synsedimentary tectonics, which in turn affects relative sea-level rise, and nutrient and detrital input. In particular, tectonics controlled the initial stage of the transgression, determining the configuration of the basin, subdivided in narrow submerged palaeotopographic lows and relatively elevated areas. Synsedimentary tectonics related to the thrust migration was also the main controlling factor in the demise of carbonate sedimentation, through the combined effect of two processes: increasing the subsidence of the basin, and triggering the terrigenous discharge from the erosion of the uplifted Apenninic relieves
2015
- History of Miocene temperate-type carbonate shelf in a compressive setting (northern Apennines), constrained by a chemostratigraphycal, microfacies and compositional study
[Abstract in Rivista]
Salocchi, AURA CECILIA; Nereo, P.; Fontana, Daniela; Conti, Stefano; Grillenzoni, Claudia; Argentino, Claudio
abstract
A detailed chemostratigraphic study associated with microfacies and compositional analysis has been performed on a early middle Miocene shallow-water shelf deposited on a wedge-top basin in the northern Apennines. More than 140 samples were collected in the representative outcrop of Torriana (Val Marecchia valley, Romagna Apennines) in order to identify factors controlling the inception and crisis of the shelf. The succession is constituted by 100 m thick mixed siliciclastic-carbonate rocks, unconformably overlying the allochthonous Ligurian units. The evolution of the carbonate shelf passed true four main phases, as shown by the detailed microfacies and compositional study, that evidence the progressive decrease of the carbonate productivity, gradually replaced by detrital sedimentation. The basal portion consists of rhodalgal rudstones and grainstones dominated by echinoids, bryozoans, coralline algae and benthic foraminifera. The progressive increase of terrigenous components and planktonic and benthic taxa marks the gradual transition to a mixed carbonate-siliciclastic shallow water-facies. The top of the succession is characterized by fine-grained sediments rich in glaucony. The main factors controlling the evolution of the shelf are increased subsidence of the basin, related to the thrust migration, and terrigenous contributions from the erosion of the rising Apennines areas. The stable isotope study show that the carbonate production has been influenced not only by regional factors, but also by a global fertility event, as the Monterey Event, recorded in the Mediterranean during the late Burdigalian - Serravallian.
2015
- Inception and crisis of a Miocene temperate-type carbonate shelf in a compressive setting (northern Apennines)
[Abstract in Atti di Convegno]
Salocchi, AURA CECILIA; Fontana, Daniela; Conti, Stefano; Fioroni, Chiara; Grillenzoni, Claudia; Argentino, Claudio
abstract
A detailed study including stratigraphy and composition has been performed on shallow-water carbonates of early-middle Miocene age deposited in a wedge-top basin in the northern Apennines. In the representative outcrop of Torriana (Val Marecchia valley, Romagna Apennines) more than 140 samples were collected in order to identify factors controlling the inception and crisis of the shelf.
The succession unconformably rests on the allochthonous Ligurian units and is constituted by up to 100 m thick carbonates and mixed siliciclastic-carbonate rocks. The basal portion consists of rhodalgal rudstones and grainstones dominated by echinoids, bryozoans, coralline algae and benthic foraminifera. It gradually passes into mixed carbonate-siliciclastic shallow water-facies, characterized by an increase in terrigenous components and planktonic and benthic taxa. The occurrence of glaucony-rich packstones with abundant planktonic foraminifera marks the transition to the upper fine-grained sediments.
Results of a detailed compositional study evidence four main phases in the platform evolution, and a progressive decreasing of the carbonate productivity, gradually replaced by detrital sedimentation.
Regional factors linked to the Apenninic tectonics seem to primarily support the eu- to mesotrophic conditions in the examined carbonate shelf. However this time interval (late Burdigallian - Serravallian) is characterized by the global fertility event, the Monterey Event, recorded also in the Mediterranean. The stable isotope study shows that this global event also influenced the carbonate production.
The inception and demise of these temperate rhodalgal-foramol carbonate sediments located in a wedge-top basin is primarily controlled by synsedimentary tectonics related to the thrust migration, through the combined effect of two processes: increasing the subsidence of the basin, and triggering the terrigenous discharge from the erosion of the uplifted Apenninic areas.
2015
- Miocene carbonate shelf in the northern Apennines (S. Marino Fm): insights from microfacies, petrography and strontium isotopes
[Abstract in Atti di Convegno]
Argentino, Claudio; Salocchi, AURA CECILIA; Fontana, Daniela; Reghizzi, M; Grillenzoni, Claudia; Conti, Stefano
abstract
A detailed stratigraphic study associated with microfacies and strontium analysis has been performed on middle Miocene shallowwater
carbonates developed in a wedge-top basin in the northern Apennines. More than 140 samples were collected in the
representative outcrop of Torriana (Marecchia valley, Romagna Apennines). It covers the entire carbonate succession from the
basal unconformity on Ligurian units to the terrigenous-rich sediments that mark the demise of the shelf. The modal analysis
allowed to quantify the main framework components: an intrabasinal carbonate fraction (biogenic), a terrigenous fraction (largely
siliciclastic) and an authigenic intrabasinal component mainly constituted by glauconitic grains.
The carbonate succession starts with massive carbonates consisting of rudstones and grainstones dominated by bryozoans and
echinoids. The basal few meters are rich in rhodolithes. The succession passes to planar-bedded grainstones to packstones with the
same fossiliferous composition. The upper part is characterized by low angle cross-bedded grainstones to packstones with high
detrital content, that gradually passes to mixed siliciclastic-carbonate sediments and finegrained hybrid arenites. An overall
increase of the terrigenous input to the basin and the progressive deepening from a shallow shelf to outer shelf-slope environment
caused the drowning of the shelf, marked by relatively high concentration of glauconitic grains. Our data indicate an almost
exclusive intrabasinal supply during deposition of the basal portion. A vertical evolution is documented by a progressive increase
in the terrigenous supply that replaces the bioclastic fraction.
Preliminary 87Sr/86Sr data obtained from 7 carbonate samples allowed us to obtain absolute ages for the lower massive portion of
the succession. For each sample we analyzed mollusk shells, bryozoans and bulk rock. Results indicate ages between 16,52-15,91
Ma, corresponding to the Burdigalian-lower Langhian interval. Comparing the values obtained from mollusk shells, bryozoans and
bulk rock from samples at the same stratigraphic level, we observe similar results.
This, according to petrographic analysis, permitted us to suppose a low diagenetic imprint of the rock.
2015
- Sedimentology and composition of sands injected during the seismic crisis of May 2012 (Emilia, Italy): clues for source layer identification and liquefaction regime
[Articolo su rivista]
Fontana, Daniela; Lugli, Stefano; MARCHETTI DORI, Simona; Caputo, R.; Stefani, M.
abstract
InMay 2012widespread sand blows formed along buried channels in the eastern sector of the Po Plain (Northern
Italy) as a consequence of a series of seismic eventswith main shocks ofMw6.1 and 5.9. At San Carlo (Ferrara) a
trench dug a few week after the earthquakes exposed sand dikes cutting through an old Reno River channel–
levee system that was diverted in the 18th century and was deposited starting from the 14th century (unit A).
This sequence overlies a Holocene muddy floodplain deposits and contains scattered sandy channel deposits
(unit B) and a Pleistocene channel sand unit (unit C). Sands with inverse and normal grading, concave layering
and vertical lamination coexisting along the dikes suggest multiple rhythmic opening and closing of the fractures
that were injected and filled by a slurry of sand during the compression pulses, and emptied during the extension
phase. The pulse mechanism may have lasted for several minutes and formed well stratified sand volcanoes
structures that formed at the top of the fractures. Sands fromdikes and fromthe various units showwell defined
compositional fields from lithoarenitic to quartz-feldspar-rich compositions. Sands from the old Reno levee and
channel fill (unit A) have abundant lithic fragments derived fromthe erosion of Apennine sedimentary carbonate
and terrigenous successions. Composition of the sand filling the dikes showclear affinities with sand layers of the
old Reno River channel (Unit A) and clearly differ from any sand from deeper Holocene and Pleistocene layers
(Unit B and C),which are richer in quartz and feldspar and poorer in sedimentary lithic fragments. Sorting related
to sediment flux variations did not apparently affect the sand composition across the sedimentary structures.
Textural and compositional data indicate that the liquefaction processes originated from a relatively shallow
source consisting of channel sands located within Unit A at 6.8.to 7.5 m depth.
2014
- Cold-seep carbonates as tracers for the evolution of the platform-basin system in the Miocene of the northern Apennines (Italy)
[Abstract in Atti di Convegno]
Salocchi, AURA CECILIA; Fontana, Daniela; Conti, Stefano; Fioroni, Chiara; Grillenzoni, Claudia
abstract
The peculiar methane-derived carbonates enclosed in pelitic and marly deposits of the Miocene inner foredeep
in the northern Apennines are useful tracers for an evaluation of tectonic and sedimentary processes in the
Miocene shelf-slope-basin system in a compressive geodynamic context. The carbonate precipitation is related
to emissions of hydrocarbon-rich fluids and it is controlled by: - tectonic events (tectonics constrains the
plumbing system, with faults and fractures serving as conduits and channelling water and methane up to the
seafloor); - climatic events (carbonate formation seems to correlate with cold periods and sea-level low-stand).
The correlation between methane-derived carbonates and climate during the Miocene in the northern Apennines
has been suggested by recent results (Fontana et al,. 2013) of a sedimentological and biostratigraphic study of
seep-carbonates and the enclosing hemipelagic Vicchio marls. The study suggests a correlation between the
carbonate precipitation and the middle Miocene cooling event (Mi3b). The ascent and emission of methane-rich
fluids may have been triggered by the pressure drop due to the eustatic fall. A detailed study of the δ18O record
of carbonates and δ13C of total organic matter in enclosing marls has been performed in order to verify a
correlative trend in correspondence of the climatic cooling event. A palaeocological study has allowed to check
the influence of these stressed environmental conditions on benthic foraminifera assemblages. Therefore
morphological, textural, biostratigraphic, geochemical studies could allow to characterize seep-carbonates
related to climatic event. Results of this study could contribute to the reconstruction of transgressive-regressive
events in the adjacent temperate-type carbonate platforms, as well as the definition of modes and rates of the
demise of carbonate deposition and the onset of clastic sedimentation.
The identification of cold phases and lowering of sea level in slope-basinal deposits and their detailed timing,
may be an useful and innovative tool for correlation with coeval shallow-water successions, and for the
reconstruction of the evolution of the Miocene platform-basin system in the compressive setting of the northern
Apennines.
2014
- Relationships between seep-carbonates, mud volcanism and basin geometry in the Late Miocene of the northern Apennines of Italy: the Montardone mélange
[Articolo su rivista]
Conti, Stefano; Fontana, Daniela; Claudio Corrado, Lucente; Gian Andrea, Pini
abstract
The Montardone mélange (Mm) is a chaotic, block-in-matrix unit outcropping in the Montebaranzone syncline in the northern Apennines. The Mm occurs in the uppermost part of the Termina Fm, the Middle-Late Miocene interval of a succession deposited in a wedge-top slope basin (Epiligurian succession). The Mm is closely associated with bodies of authigenic carbonates, characterized by negative values of δ13C (from -18.22 to -39.05 ‰ PDB) and chemosyntethic benthic fauna (lucinid and vesicomyd bivalves). In this paper we propose that the Mm is a mud volcano originated by the post-depositional reactivation and rising of a stratigraphically lower mud-rich mass-transport body (Canossa-Val Tiepido sedimentary mélange or olistostrome) triggered by fluid overpressure. We base our conclusion on: 1) the Mm pierces the entire Termina Fm and older Epiligurian units and represents the direct continuation of the underlying Canossa-Val Tiepido mélange; 2) the geometry and facies distribution of the Montebaranzone sandstone body, which are compatible with a confined basin controlled by the rising of the Mm; 3) the systematic presence of large-scale (lateral extension 300-400 m) seep-carbonates associated with the mélange, suggesting a persistent gas-enriched fluid vent from the ascending overpressured mud; 4) blocks and clasts sourced from the Mm, hosted by the authigenic carbonates, conveyed by ascending mud and gas-enriched fluids.
The Mm represents one of the few fossil examples of reactivation of a basin-scale sedimentary mélange (olistostrome); a three-stage model showing mechanisms of Mm raising is proposed.
2014
- The evolution of the Miocene platform-basin system in the northern Apennines: what can we learn from seep-carbonates?
[Abstract in Rivista]
Grillenzoni, G.; Conti, Stefano; Fioroni, Chiara; Fontana, Daniela; Salocchi, A.
abstract
Cold seep-carbonates documenting the expulsion of fluids enriched in methane have been identified in a variety of
basin margins and tectonic-sedimentary settings. A number of geological factors influences methane seep activity, but
primarily regional and local tectonics, mainly at the deformation front of accretionary prism and inner foredeep.
Tectonics constrains the fluid circulation system, with faults and fractures serving as conduits and channelling water
and methane up to the seafloor. Recent studies suggest that seep-carbonates occurrence is also controlled by climatic
changes and their formation seems to correlate with cold periods and sea level low-stand. A drop of the hydraulic
pressure on the plumbing system during sea level lowering in glacial phase could increase methane flows at seeps,
inducing carbonate precipitation. The correlation between methane-derived carbonates and climate has been recently
suggested for the Miocene of the northern Apennines by means of a sedimentological and biostratigraphic study of
seep-carbonates and the enclosing hemipelagic marls (Vicchio Formation) (Fontana et al., 2013). The study suggests a
correlation between the carbonate precipitation and the middle Miocene glacial cooling event (Mi3b). The triggering of
the ascent and emission of methane-rich fluids may be related to the eustatic fall and in turn to the water pressure
drop. A detailed stratigraphic and biostratigraphic study of seep-carbonates and enclosing marls in foredeep deposits of
the Tuscan-Romagna Apennines has allowed a precise dating of seepage in slope and basinal successions. The analysis
of the δ18O and δ13C records of carbonates, δ13Corg excursion of organic matter and TOC on the marls enclosing the
authigenic carbonates has been performed in order to verify a correlative trend in correspondence of the climatic
cooling event. A paleoecological study on benthic foraminifera assemblages has also allowed to detail these peculiar
environments. The events defined from this study in basinal deposits have been correlated with depositional changes
and discontinuity surfaces in the adjacent temperate-type carbonate platforms, and have contributed to the definition of
modes and rates of the demise of carbonate deposition. The identification of cold phases and lowering of sea level in
slope-basinal deposits and their detailed timing, may be a useful tool for correlation between deep depositional setting
and coeval shallow-water successions. This approach may also provide important constrains in the reconstruction of the
evolution of the Miocene platform-basin system in this complex compressive setting of the northern Apennines.
Fontana D., Conti S., Grillenzoni C., Mecozzi S., Petrucci F. & Turco E. 2013. Evidence of climatic control on
hydrocarbon seepage in the Miocene of the northern Apennines:
2013
- Composition of sands injected during the seismic crisis of May 2012 at San Carlo, Ferrara (Italy)
[Relazione in Atti di Convegno]
Fontana, Daniela; Lugli, Stefano; MARCHETTI DORI, Simona; Caputo, R.; Stefani, M.
abstract
We analyzed the petrographic composition of sands injected through fractures during the seismic crisis of May 2012 along the paleo-Reno River and sands from subsurface deposits at San Carlo (Ferrara) to define their provenance and provide a contribution to the understanding of the liquefaction mechanism.
The sampling of sand has been done in a trench dug immediately after the seismic event, which allowed the detailed observations of the fluvial sedimentary sequence and of sand dikes down to the depth of about 6 m (Caputo et al., 2012). We sampled also two sand horizons in the subsurface that were crossed by drillings up to the depth of 50 m.
A total of 20 sand samples were analyzed: 9 from the sand dikes, 6 from the cores crossing the upper sand horizon (8-10 m depth) and the lower sand layer dating back to the uppermost Pleistocene, 1 from the paleo-channel fill of the Reno River (diverted at the end of 18th century) and 4 from the modern sands of the present-day Reno River.
The sand samples were analyzed for their grain size distribution and by point-counting under transmitted light microscopy on the 0.125–0.250 mm fraction, according to the Gazzi-Dickinson method (Zuffa, 1985). At least 300 grains were point counted for each section to achieve modal composition.
On the basis of the classification diagram Q+F, L, C, the sands show a defined trend from lithoarenitic to quartz-feldspar-rich composition. In particular, the sands from the modern Reno River are the most lithoarenitic. The lithoarenitic fragments derive mostly from the erosion of sedimentary rocks such as siltstone, shale and limestone.
The sands filling the dikes show compositions similar to that of the modern Reno River with a slight enrichment in quartz and feldspar grains.
The single sand dikes at different depths show minor, non-systematic, composition variations, in one case due to carbonate content change in another due to quartz and lithic fragments variability.
The sand sample from the paleo-Reno channel fill shows a composition similar to those of the dikes and is slightly impoverished in lithic fragments compared to the modern Reno River sands.
The core samples are enriched in quartz and feldspar and in some cases show a distinct content of metamorphic rock fragments, that may indicate a possible provenance from the Po River or maturation as consequence of climatic weathering that occurred during the last glacial stage (Lugli et al., 2007).
The sand from the dikes fill appear clearly different from the deep sand sampled from the cores at depth, suggesting a relatively shallow source for the blowouts.
Modal analyses of sands from the Modena Plain streams indicate that their provenance signal can be clearly distinguished and that the sand composition of major rivers has not varied during the last ~7 kyr (Lugli et al., 2007). It follows that provenance of older sediments buried in the floodplain can be determined by a simple comparison with modern sand composition. This indicates that we have a powerful tool to reconstruct the evolution of the drainage system that is pivotal for the recognition of potential areas prone to hazardous sand liquefaction phenomena.
2013
- Evidence of climatic control on hydrocarbon seepage in the Miocene of the northern Apennines: The case study of the Vicchio Marls
[Articolo su rivista]
Fontana, Daniela; Conti, Stefano; Grillenzoni, Claudia; Mecozzi, S.; Petrucci, F.; Turco, E.
abstract
The Vicchio outcrop in the Tuscan Apennines contains excellent exposures of a Miocene methane-derived carbonate system, made up of more than 80 carbonate bodies enclosed in marly sediments. Facies analysis, composition and a detailed biostratigraphic study of the carbonates and enclosing Vicchio Marls allowed us to document the role of climatic changes and eustasy on seepage in these ancient deposits. Results of our study indicate that the stratigraphic horizon bearing seep-carbonates is constrained by two planktonic foraminiferal events, the Acme End (AE) of Turborotalita cf. T.quinqueloba (13.75Ma) and the Acme1 Beginning (A1B) of Paragloborotalia siakensis (13.32Ma), encompassing about 400,000 years. The AE of T. cf. T.quinqueloba approximates the mid-Miocene global cooling event (Mi3b), as defined by the δ18O maxima (13.78Ma). The glacio-eustatic sea level drop associated with this cooling event is estimated to be approximately 60m. Assuming that the highest rates of glacio-eustatic sea level fall coincide with δ18O maxima, the timing of the seepage onset (at about 13.75Ma) is concomitant with the phase of sea level-lowering. The ascent and emission of methane-rich fluids may have been triggered by pressure drop due to the eustatic fall associated with the Mi3b event. The moderate intensity of fluid expulsion is suggested by the lack of brecciation, by the scarcity of detrital particles in the carbonates and by the pervasive occurrence of carbonate in the enclosing marls. This type of seepage differs from focused fault-confined fluid flows, typical of other tectonically controlled Apenninic seep-carbonates. © 2013 Elsevier Ltd.
2013
- Seep-carbonate case studies as highlights in the evolution of the Miocene of northern Apennines
[Relazione in Atti di Convegno]
Grillenzoni, Claudia; Conti, Stefano; Fontana, Daniela; Fioroni, Chiara
abstract
Different case studies of seep-carbonate outcrops in the Northern Apennines show that an accurate timing of precipitation, and the identification of processes of ascent of methane-rich fluids, are important points for understanding and estimating the complex interplay of tectonics and climate changes during the Miocene of the northern Apennines.
2012
- Seep-carbonates as indicators of global cooling events (Miocene, northern Apennines
[Articolo su rivista]
Grillenzoni, Claudia; Conti, Stefano; Fontana, Daniela; Turco, Elena
abstract
Recent studies in dating seep-carbonates suggest that their occurrence is controlled by climatic changes (TEICHERT et alii 2003). KIEL (2009) suggests that this correlation exists from the late Jurassic to Recent, and shows a statistically relevant correlations between the frequency of seep-carbonates in the past 150 Ma and low deep-water temperature and low sea- levels. In the Miocene of the northern Apennines, the abundance and the extent of the seep-carbonates from different tectonic-sedimentary settings, foredeep to satellite basins, provide a rare opportunity to study the tectonic and/or climatic controls on seepage (CONTI & FONTANA, 1999 A detailed stratigraphic and biostratigraphic study of carbonates and enclosing marls indicates that the stratigraphic horizon bearing seep-carbonates lies between the T. cf. T. quinqueloba AE (13.75 Ma) and the P. siakensis A1B (13.32 Ma) encompassing a time interval of about 400.000 years. Since the AE of T. cf. T. quinqueloba approximates the mid- Miocene global cooling event, we infer that the beginning of the seep-carbonate precipitation in the Vicchio Marls seems to be related to this climatic event (Fig. 2). We assume that the ascent and emission of methane-rich fluids may have been triggered by the pressure drop due to the eustatic fall associated with the Mi3b event, estimated in about 60 m (HILGEN et alii, 2009). A drop of the hydraulic pressure on the plumbing
2011
- Possible Relationships between Seep Carbonates and Gas Hydrates in the Miocene of the Northern Apennines
[Articolo su rivista]
Conti, Stefano; Fontana, Daniela
abstract
In the Miocene of the northern Apennines, a widespread carbonate precipitation was induced by the expulsion of methane-rich fluids. Numerous outcrops of carbonate masses share sedimentological, textural and geochemical features with present-day gas hydrate-associated carbonates. We hypotesize the contribution of paleo-gas hydrate destabilization on the base of the heavy oxygen isotope signature, the presence of distinctive sedimentary features (breccias, pervasive non-systematic fractures, soft sediment deformation), the close association between seep-carbonates and sedimentary instability and the huge dimensions of seep-carbonates bearing brecciated structures.
2011
- Stratigrafia e analisi di facies della successione continentale permiana e triassica della Nurra: confronti con la Provenza e ricostruzione paleogeografica
[Articolo su rivista]
A., Ronchi; G., Cassinis; M., Durand; Fontana, Daniela; G., Oggiano; C., Stefani
abstract
Nella Sardegna nord-occidentale è esposta in modo spettacolare, anche se discontinuo, una successione continentale post-varisica rappresentata da depositi terrigeni intercalati a prodotti vulcanoclastici.Oggetto di questo lavoro sono i caratteri stratigrafici, sedimentologici e composizionali della successione terrigena affiorante nell’area della Nurra, a nord di Alghero, tra Punta Lu Caparoni a nord e Cala Viola a sud e il loro confronto litostratigrafico con la successione provenzale. L'intera successione è costituita da conglomerati, arenarie e peliti di colore prevalentemente rosso, ricca in clasti di derivazione vulcanica (in particolare dai porfidi delle vulcaniti inferiori); si tratta di una sequenza che evolve da ambiente di conoide aun sistema fluviale di tipo braided e quindi passa a un ambiente fluviale meandriforme. La parte sommitale della successione (ciclo III) è marcata da una netta discontinuità rappresentata da un conglomerato quarzoso (conglomerato del Porticciolo) esteso a scala regionale, che passa superiormente ad una successione costituita da arenarie e subordinate peliti, con alternati influssi fluviali e marini. I depositi continentali permiani della Provenza sono molto sviluppati e costituiscono il riempimento di quattro bacini principali sedimentari disposti intorno al Massiccio varisico dei Maures: da est ad ovest sono i bacini dell’Estérel, di Bas-Argens, di Le Luc e di Cuers-Toulon. Una correlazione litostratigrafia tra quest’ultimo e la successione della Sardegna nord-occidentale è stata recentemente proposta In Provenza sono stati riconosciuti due cicli vulcanici: il primo, calcalcalino affiora sporadicamente solo nel Bacino dell’Estérel (formazione de L’Avellan) ed è testimoniato dai ciottoli di vulcaniti presenti nella formazione di Les Salettes nel Bacino di Toulon-Cuers; il secondo, successivo e molto più diffuso, soprattutto nel Bacino
dell’Estérel, è rappresentato da numerosi episodi ignimbritici, filoni e lave ad affinità alcalina. Il limite Permo-Triassico è generalmente collocato alla base del cosiddetto Gruppo “Buntsandstein” e la relativa discordanza rappresenta uno hiatus di circa 10-15 Ma che comprende gran parte del Lopingiano e
dell’Induano. La sedimentazione triassica si distingue chiaramente da quella permiana poiché riflette un drastico cambiamento da un sistema di drenaggio in singoli bacini, caratteristico della paleogeografia permiana, ad un sistema molto più ampio e diretto verso SO. I più antichi depositi clastici triassici, soprattutto nell’area di Tolone, sono rappresentati da sedimenti tardo induani-olenekiani (Dieneriano-Smithiano), mentre i più giovani
tra questi sono ascrivibili all’Anisico inferiore .
2010
- A contribution to the reconstruction of Miocene seepage from authigenic carbonates of the northern Apennines (Italy)
[Articolo su rivista]
Conti, Stefano; Fontana, Daniela; S., Mecozzi
abstract
Authigenic carbonates from outcrops of the northern Apennines consist of small and irregular lenses and exhibit numerous features indicative for cold-seep settings. Detailed petrographic, mineralogical and geochemical studies from two Miocene deposits are presented. The first carbonate outcrop named Fosso Riconi is located in the foredeep basin of the Apenninic chain whereas the second deposit represents a satellite basin called Sarsetta. The stable isotope data from specific carbonate minerals show a wide range of values well known from other paleoseeps of the Apennine Mountains. From all carbonates analyzed during this study the majority of seep carbonates are formed by low-Mg calcite and ankerite. Those minerals have δ13C values between -7 and -23‰ V-PDB suggesting variable amounts of carbonate derived from oxidized methane, from seawater (DIC), and from sedimentary organic matter. Dolomite samples have the lowest δ13C values (-30.8 to -39.0‰ V-PDB) indicating methane as the main carbon source.The results from this study indicate an evolutionary formation of the seeps and development of the authigenic carbonates, influenced by the activity of chemosynthetic organisms from which large lucinid clams are preserved. Bioirrigation of those clams controlled the sediment-water exchange, and is here considered as an explanation for the anomalous Mg content of the calcite. We hypothesize that seep-carbonates are formed during periods of active methane-rich seepage, whereas during periods of slow seepage carbonate formation was reduced. Despite different geological settings, the two examined deposits of Sarsetta and Fosso Riconi show similar features, suggesting that the pattern of fluid circulation at both seep sites played a major role in their carbonate formation.
2010
- Facciamo Ordine! Simmetrie e Asimmetrie tra Natura e Pensiero.
[Altro]
Brunetti, Rossella; Bandieri, Paola; Fontana, Daniela
abstract
La Natura che ci circonda e di cui facciamo parte mostra una forte propensione alla simmetria, anche se alcune fondamentali asimmetrie condizionano il nostro mondo e i nostri gusti.Percorso per la scuola media superiore: ha forte valenza interdisciplinare e conduce i ragazzi verso le simmetrie e le asimmetrie attraverso gruppi dei, fregi, dei rosoni e gruppi cristallografici, i fenomeni astrofisici, i minerali ed i fossili.Percorso per le scuole elementari: si propone di avvicinare i bambini di IV e V elementare ad un concetto così astratto quale la simmetria, attraverso esperienze di vita quotidiana e attività manuali.Conferenze pubbliche: ciclo di conferenze divulgative che spaziano tra matematica, astrofisica, scienze naturali ed anche la musica.
2010
- Late Miocene seep-carbonates and fluid migration on top of the Montepetra intrabasinal high (Northern Apennines, Italy): Relations with synsedimentary folding
[Articolo su rivista]
Conti, Stefano; Fontana, Daniela; Mecozzi, S.; Panieri, G.; Pini, G. A.
abstract
During the Miocene, hydrocarbon seep-carbonates located atop intrabasinal highs and associated with sediment instability, formed commonly at the deformation front of the Northern Apennine collisional orogen. The parallelism between the structural trend and the distribution of seep-carbonates suggests a close relationship between tectonics and gas/fluid emission.The “Montepetra intrabasinal high” was formed during the closure stage of the foredeep, being related to the synsedimentary growth of an anticline. Field geometry suggests that detachment folding was the leading mechanism of anticline growth and synsedimentary instability along the anticline flanks. Ten different bodies of seep-carbonates occur in the Tortonian-early Messinian sediments: nine in the hinge zone and one in the southern backlimb of the anticline. Foraminiferal study, geochemistry, facies investigation and the three-dimensional geometry of carbonate bodies with respect to the encasing terrigenous sediments indicate a protracted (late Tortonian-early Messinian) activity of fluid migration with re-mobilization and ascent of sediments from the core of the anticline, stabilization of chemosynthesis-related communities, and in-situ brecciation. Seepage atop the intrabasinal high was fed by different circuits: one related to the compaction-dewatering of shallow (Tortonian-early Messinian) sediments, and a deeper one related to the deformation of the anticline core and to the activity of detachment surfaces and of faults propagating through the sedimentary cover.
2009
- Cold-seep carbonates: fossil archives of changes in seepage activity and fluid. composition through the Miocene. In: Geoitalia 2009. Epitome, Vol. 3, 89. FIST.
[Relazione in Atti di Convegno]
Mecozzi, Silvia; Conti, Stefano; Fontana, Daniela
abstract
The precipitation of authigenic carbonates
2009
- Discriminating fluid sources in Miocene cold seep systems using REEs in authigenic carbonates
[Abstract in Rivista]
Mecozzi, S.; Bayon, G.; Rongemaille, E.; Conti, Stefano; Fontana, Daniela
abstract
Authigenic carbonates are a common feature in cold seep environments, where fluids enriched in methane and other hydrocarbon gases escape from the seafloor. Seep-carbonates have been reported worlwide both in modern and ancient sedimentary deposits. In the Northern Apennines (Italy), numerous outcrops of seep-carbonates are particularly well-preserved. Evidences from paleoecological, sedimentological, geochemical and isotopic (O and C stable isotopes) analyses cleary show that they were derived from the microbial oxidation of methane-rich fluids. REE patterns and abundances in fossil seep-carbonates may provide additional informations for better constraining the origin and the composition of the fluids from which they have precipitated.Here, we report REE data for a series of Miocene carbonate samples recovered from various geological settings in the Northern Apennines. Samples were leached with 5% HNO3, prior to analysis by SF-ICPMS using the Tm addition method [1]. Total REE concentrations (ΣREEN) in our studied carbonates are very similar to those reported for modern authigenic carbonates, suggesting negligible post-depositional diagenetic alteration. The shale-normalized REE patterns vary significantly amongst the different authigenic carbonate samples analysed in this study. These data indicate that they were formed from fluids having distinct REE signatures. These results, coupled with other geochemical, petrographic and mineralogical data, allow us to reconstruct the variation of fluid seepage activity in the Northern Appenines during the Miocene.
2009
- I vulcani di fango dell’Appennino modenese
[Capitolo/Saggio]
Conti, Stefano; Fontana, Daniela
abstract
I vulcani di fango rappresentano un importante fenomeno
2009
- Investigation of miocene cold seep sources using rare earth element in authigenic carbonates
[Relazione in Atti di Convegno]
Mecozzi, Silvia; G., Bayon; E., Rongemaille; Conti, Stefano; Fontana, Daniela
abstract
Seep-carbonates are described
2009
- Multiproxy approach to the stydy of Croce della Moggiona cold seep-carbonates (Northern Apennines)
[Relazione in Atti di Convegno]
Mecozzi, Silvia; Birgel, D.; Peckmann, J.; Conti, Stefano; Fontana, Daniela
abstract
Seep-carbonates are described in both the present day marine environments and in the sedimentary record of ancient basins. They are the result of microbially-mediated processes that occur on the seafloor where hydrocarbon-rich fluids are seeping. These carbonate bodies have received considerable attention in the international scientific community because they may provide a clue to investigate the origin and the composition of the fluids from which they have precipitated. In the Northern Apennine foredeep, seep-carbonates are concentrated in pelitic successions from different settings. Seep carbonates occur in large turbiditic bodies (Mt. Cervarola and Marnoso-arenacea Formations) and in slope hemipelagites (Vicchio and Verghereto Marls, and Ghioli di letto mudstones).In this study we present evidence for a long time of hydrocarbon seepage during the Middle Miocene in the form of newly discovered occurrences of carbonate bodies and concretions. About ninety authigenic carbonate bodies occur in the examined Fosso Riconi outcrop. Carbonates are irregularly scattered, both laterally and vertically, and have irregular shapes and geometries, varying from stratiform to amygdaloid, lenticular bodies and pinnacles. The thickness vary from 50 dm to 7-8 m, with lateral extension ranging from 1 to 3 m. Carbonate lithologies consist of marly limestones and calcareous marls. The lateral conctact with host sediments varies from sharp to transitional and interfingering. The marly limestone, calcareous marl lithologies are typically associated with abundant fossil remains, mainly consisting of thick recrystallized closed shells and moulds of lucinid and vesicomyid-like clams and rare and small gastropod shells. Lucinids and vesicomyids are infaunal ad semi-infaunal bivalves living in cold-seep areas and sustained by mutual symbiosis with sulphide-oxidizing bacteria. The authigenic carbonate mineralogy is dominated by low Mg-calcite, ankerite, and dolomite. Petrographic observations show complex facies relationships, as indicative of different stages in seep-carbonates growth. Stable isotope analyses of these nodules show depleted δ13C values which are consistent with the formation of carbonates in a cold-seep setting. Thus, the Fosso Riconi carbonates exhibit numerous characteristics (mineralogy, sedimentary fabrics, fossil assemblages) found at modern and ancient hydrocarbon seeps.The objectives of this contribution are to investigate the nature and source of the fluids associated with Fosso Riconi carbonate precipitation and to delineate an evolutionary model of the formation and development of these seep-carbonates.We suggest that examined seep-carbonates may be a consequence of episodes of varying fluid-venting rates.
2009
- Northern Apennines authigenic carbonates: tracers of changes in cold seep activity
[Relazione in Atti di Convegno]
Mecozzi, Silvia; Conti, Stefano; Fontana, Daniela
abstract
Seep- carbonates are described
2009
- Reconstruction of Miocene fluid seepage activity in the northern Apennines (Italy) using authigenic carbonates
[Relazione in Atti di Convegno]
Mecozzi, S.; Conti, Stefano; Fontana, Daniela
abstract
Miocene fluid flow...
2009
- Seep-carbonates at the top of a growing anticline: the “Montepetra structural high”, Late Miocene of Northern Apennines (Italy)
[Relazione in Atti di Convegno]
Conti, Stefano; Fontana, Daniela; Panieri, G.; PINI G., A; Mecozzi, S.
abstract
During the Miocene,
2009
- Terra Inquieta: Scienza per conoscere, tecnologia per prevenire le catastrofi naturali
[Esposizione]
Brunetti, Rossella; Fontana, Daniela
abstract
La Terra è una cosa viva, in continua evoluzione. Il pianeta mostra frequentemente l’incontenibile energia associata ai suoi eventi di trasformazione. Tsunami, eruzioni vulcaniche, frane, alluvioni, terremoti e grandi cambiamenti climatici producono effetti planetari che, indirettamente o direttamente, coinvolgono tutti noi nell’arco di una singola vita. Purtroppo ci si accorge di violare gli equilibri della Terra e di sottovalutare le sue costanti trasformazioni solo in occasione dello scatenarsi di quegli eventi naturali che, spesso, diventano catastrofi unicamente per causa umana.La scienza aiuta a trovare una giustificazione a una violenza distruttiva che altro non è che la dimostrazione che la Terra è un pianeta attivo. Per capire come e perché si scatenano i fenomeni che tanto ci spaventano, si deve passare attraverso la ricostruzione degli eventi naturali del passato e del presente alla luce delle attuali conoscenze scientifiche, scoprendo che non esistono vulcani assassini o onde killer, ma solo l’incapacità umana di convivere armonicamente con il pianeta. La tecnologia offre un valido aiuto ad una serena convivenza con gli eventi naturali, ma solo a patto che gli insediamenti e le attività umane mettano in atto comportamenti responsabili nei confronti dell’ambiente.Autorevoli scienziati, divulgatori ed esperti di Protezione civile guideranno il pubblico in tema di comprensione, monitoraggio, prevenzione e gestione di grandi eventi naturali raccontando, nell’occasione degli incontri, anche di sé stessi come scienziati, tecnici e promotori di cultura scientifica. I relatori individuati sono esperti ai massimi livelli nell'ambito della ricerca scientifica ( Prof. Enzo Boschi, docente di sismologia all'Università di Bologna), della divulgazione (Dott. Alberto Angela, Dott. Mario Tozzi (da confermarsi)), della Protezione civile (Guido Bertolaso (da confermarsi)).1. Per bambini a frequenza libera e scuole elementariDue incontri con gli esperti alla Biblioteca Delfini (numero chiuso, massimo 30 partecipanti).Un laboratorio itinerante da realizzarsi in due incontri presso una o più scuole elementari di Modena (su prenotazione, da confermarsi).2. Per le scuole superioriDopo una lezione introduttiva, le classi partecipanti lavoreranno su testi divulgativi, approfondendo un particolare aspetto scientifico o tecnologico delle catastrofi naturali e della loro previsione e prevenzione. Insegnanti e studenti potranno contare sui libri distribuiti in omaggio (per il suo carattere divulgativo, il libro adottato sarà M. Tozzi, Catastrofi, 250 anni di lotta tra l'uomo e la natura, Rizzoli 2005), oltre che sulla consulenza degli esperti esterni e dei docenti di UniMoRe promotori del progetto. La Biblioteca Delfini fornirà consulenza in merito alla documentazione scientifica a carattere divulgativo.A seguito degli incontri introduttivi e delle attività svolte in classe, i ragazzi realizzeranno un'intervista collettiva guidata a uno scienziato, per poi dedicarsi alla redazione di un articolo di divulgazione scientifica rispettando un format giornalistico. Nella giornata conclusiva le classi presenteranno i lavori prodotti.Il progetto è a numero chiuso con prenotazione obbligatoria fino ad un massimo di 150 studenti.3. Per la cittadinanzaQuattro conferenze serali seguite da un dibattito tenute in prestigiose sedi modenesi legate alla promozione culturale. Direzione scientifica e organizzazione: Rossella Brunetti (UniMoRe, Dip. di Fisica), Daniela Fontana (UniMoRe, Dip. di Scienze della terra), Gianantonio Battistuzzi (UniMoRe, Dip. di Chimica), Rodolfo Cecchi (UniMoRe, Dip. di Ingegneria Meccanica, dell’Ambiente e del Territorio); Meris Bellei, Angela Pacillo, Cinzia Pollicelli (Biblioteche del Comune di Modena).
2008
- Authigenic seep-carbonates cementing coarse-grained deposits in a fan-delta depositional system (middle Miocene, Marnoso-arenacea Formation, central Italy)
[Articolo su rivista]
Conti, Stefano; Fontana, Daniela; C. C., Lucente
abstract
Seep-carbonates (13C-depleted) are present at different levels within the Miocene terrigenous succession of Deruta (Marnoso-arenacea Formation, central Italy). They are associated with pebbly sandstones and conglomerates in a tectonically active fan-delta slope depositional system. Most of them are included in slide/slump horizons as scattered blocks. The occurrence of seep-carbonates is clear evidence of flow of methane-rich fluids pervading the sediments. Fluids, probably of biogenic origin, may have reached the sea-bottom through thrust faults and selectively infiltrated the more permeable coarse-grained horizons deposited along the slope. Different stages of fluid emissions are documented: slow flux stage, corresponding to the development of large carbonate bodies and dense chemosynthetic communities, and fast fluid flow associated with intense carbonate brecciation, pipes and veins. Large amounts of authigenic carbonates are reworked by slope failures triggered by tectonics and fluids reducing sediment strength; in situ cementation of slide blocks may also have occurred due to remobilization of methane-rich fluids by mass-wasting processes.
2008
- Fluid expulsion and typology of seep-carbonates in the northern Apennines.
[Relazione in Atti di Convegno]
Mecozzi, Silvia; Conti, Stefano; Fontana, Daniela
abstract
Miocene seep-carbonates have been reported from marine sedimentary successions of the northern Apennines in the form of huge isolated carbonate bodies (type 1) and numerous horizontally and vertically scattered marly-calcareous lenses (type 2) (Conti and Fontana, 2005 and references herein). They are recognized by their peculiar palaeoecological, sedimentological, compositional and isotopic features as products of the microbial oxidation of methane-rich fluids and represent an excellent example of carbonate bodies interpreted as the remains of ancient cold seeps. In the Apenninic chain, the abundance and the extent of the outcrops provide a rare opportunity to study the geometry, facies distribution and internal structures of fossil seep-carbonates. The main parameters which control the composition and development of a carbonate body are the methane pressure in interstitial sedimentary fluids, the flux discharge and rate in the venting zone, and the evolutionary path of the rising fluids (Roberts, 2001). Mineralogical, petrographic analyses, carbon and oxygen isotopic compositions of type 1 and 2 carbonate samples indicate that different mechanisms of hydrocarbon fluid expulsion and variations in the upward methane flux control carbonate types and mineralogy.Mineralogical analyses of type 1 carbonate samples indicate that dolomite and ankerite represent the dominant phases, while low-Mg calcite is the type 2 dominant carbonate phase. The carbon and oxygen isotopic compositions of the carbonates display very large ranges, from -10‰ to -55‰ V-PDB, and from -3‰ to 6‰ V-PDB, respectively. Seep-carbonate type 1 appear significantly depleted in δ13C (ranging from -30‰ to -55‰ V-PDB) while seep-carbonate type 2 are only moderately depleted (δ13C varying from -10‰ to -23‰ V-PDB). Petrographic observations show complex facies relationships, as indicative of different stages in seep-carbonates growth.Type 1 seep-carbonates could be related to constant and discrete fluid seepage conditions while type 2 could be explained by variations in the upward methane flux (increasing, decreasing flow rates). The intraformational and rarely extraformational polygenic breccias which are often observed in the basal portions of type 1 seep-carbonates could indicate phases of violent venting of gaseous-rich fluids. The explosive escaping of carbon-rich fluids interrupted the conditions of constant fluid seepage and caused brecciation of the carbonate body. Our presentation will report the result of a detailed field observation of the two types of seep-carbonates coupled with geochemical, petrographic and mineralogical studies.
2008
- Fluid flux and migration conditioning Miocene-seep carbonate precipitation in the northern Apennines.
[Relazione in Atti di Convegno]
Conti, Stefano; Fontana, Daniela; Mecozzi, S.
abstract
In the Miocene satellite and foredeep basins of the northern Apennines, numerous outcrops of carbonate bodies share specific palaeoecological, sedimentological, compositional and isotopic features with present-day seep-carbonates.These carbonates occur in large turbiditic bodies (Mt. Cervarola and Marnoso-arenacea Formations) and in slope hemipelagites (Vicchio and Verghereto Marls, and Ghioli di letto mudstones). Apennine hydrocarbon seep-carbonates form isolated, irregularly-shaped masses of limestones with distinctive fabrics, specialized fossil fauna (chemosymbiotic clams and mussels) and exibit typical 13C-depleted signatures indicative of methane influence during precipitation. Several characteristics allow two type of seep-carbonates to be distinguished in the field (type 1 and 2). The type 1 is composed of a horizontal repetition of decametric to heptometric carbonate bodies, lenses and pinnacles. The basal portions of these huge bodies are strongly brecciated, made up of intraformational and rarely extraformational polygenic breccias. The type 2 is made of numerous and small marly-calcareous lenses, irregular column-like bodies aligned along bedding strikes, or horizontally and vertically scattered and not related to a precise stratigraphic level. Many of them consist of several lenticular units vertically stacked and separated by thin pelitic levels, thus suggesting periodic growth. Carbon isotope measurements show that carbonates from type 1 and 2 are typically depleted in 13C but the amount of depletion seem to differ between them. Therefore type 1 seep-carbonates appear significantly depleted in δ13C (δ13C ranging from -30‰ to -55‰ relative to the PDB standard) while type 2 seep-carbonates are only moderately depleted (δ13C varying from -10‰ to -23‰ relative to the PDB standard). Concerning oxygen isotopic measurements type 1 seep-carbonates seem to be enriched in δ18O (δ18O ranging from 1‰ to 6‰ relative to the PDB standard) whereas type 2 seep-carbonates show a more scattered range (δ18O varying from -3.00‰ to 2‰ relative to the PDB standard). Our presentation will report the result of detailed field observation of the two types of seep-carbonates coupled with petrographic, mineralogical and geochemical studies. In particular we discuss the isotope geochemistry, the mineralogy, the geometry in context with the precipitation and recrystallisation processes of the carbonates, the origin of carbon rich fluids and with different mechanisms of seep-carbonate formation.
2008
- GEO-benessere, approfondimenti e incontri su Geologia, Salute e Wellness. Museo Universitario “Gemma 1786”, Dipartimento di Scienze della Terra, 19-20 aprile 2008
[Esposizione]
Bertacchini, Milena; Fontana, Daniela; Galli, Ermanno; Rossi, Antonio
abstract
Terme, fanghi, salse e grotte termali e il benessere che da questi deriva, o meglio, il GEO-benessere, se si considerano le origini geologiche di questi trattamenti di salute e di wellness, sono i temi che il Museo Universitario "Gemma 1786" del Dipartimento di Scienze della Terra ha affrontato con l'iniziativa dal titolo "GEO-benessere, approfondimenti e incontri su Geologia, Salute e Wellness", organizzata nell’ambito della rassegna “Musei da gustare 2008” della Provincia di Modena.L’iniziativa è stata organizzata con il contributo della Fondazione Cassa di Risparmio di Modena. Hanno collaborato all'iniziativa: Associazione Interculturale Dawa; Grotta del Vento, Fornovolasco (LU); Grotta Giusti Natural Spa Resort, Monsummano Terme (PT); ISTEC-CNR; IGG-CNR; Riserva Naturale Salse di Nirano (MO); Riserva Naturale “Macalube di Aragona” (AG); Smalticeram; Terme della Salvarola, Sassuolo (MO); Terme di Castel San Pietro (BO); Terme di Sant'Agnese, Bagno di Romagna (FC); Università di Bologna; Università di Modena e Reggio Emilia: Dipartimento Scienze della Terra; Dipartimento di Scienze Farmaceutiche - Eurit, Gruppo Colorobbia
2008
- Geological Processes and products related to Miocene cold seeps
[Relazione in Atti di Convegno]
Mecozzi, S.; Artoni, A.; Conti, Stefano; Fontana, Daniela
abstract
Cold seeps are commonly associated with the presence of authigenic carbonates, due to interaction between hydrocarbons-rich fluids, geological processes (tectonics, sediment instability, chaotic bodies) and biological activity.In these environments hydrocarbon-rich fluid emissions support flourishing communities of mussel, clam bivalves, gastropods, tube worms and bacterial mats, which rely on chemosynthetic energy for their metabolism. The formation of authigenic carbonates at cold vents is closely related to the anaerobic oxidation of methane (AOM) which releases sulfide and bicarbonate into the pore water. Seep-carbonates have been reported worldwide both in modern and ancient sedimentary deposits. Fossil seep-carbonates provide unique archives of focused methane seepage in the geological record. by their geochemical, petrographic, mineralogical, isotopic and structural inventory. In the northern Apennines numerous outcrops of seep-carbonates are excellently exposed. In the Apenninic chain, the abundance and the extent of the outcrops provide a rare opportunity to study the geometry, facies distribution and internal structures of fossil hydrocarbon-derived carbonates. They were recognized as products of the microbial oxidation of methane-rich fluids on the basis of their megafaunal assemblages and geological, compositional and isotopic attributes Our investigations have been carried out by means of detailed field observations of the northern Apennine seep-carbonates coupled with geochemical, petrographic, mineralogical and isotopic studies.In particular, this multidisciplinary approach permits an assessment of the pathways and origin of the fluids from which carbonates have precipitated (marine seawater source, marine organic matter source, thermogenic and biogenic methane); the final aim is the creation of a model for fossil seep-carbonate formation and development. The case study of the Salsomaggiore Ridge has been reported. This Ridge, a thrust-related anticline forming inside the middle Miocene foredeep at the outermost front of the Apenninic orogenic wedge, revealed a patchy distribution of mound- to pod-shaped seep-carbonates which, in few cases, preserve the deeper fluids feeding system consisting in a randomly arranged web of cm- to dm-sized tube conduits. The seep-carbonate facies and morphotypes are highly variable; either or not associated to typical macrofauna, they both encrust and cement siliciclastic turbidites or they inter-finger with hemipelagic marls. Seep-carbonates appear also brecciated with mottled and vuggy fabrics; a chaotic body reworks the seep-carbonates and other intra-basinal clasts. Stack of mound-shaped and bivalves-rich seep-carbonates are mainly located on the northern limb of the anticline while cementing and inter-fingering carbonates predominate on the southern limb of the same anticline. Northern and southern limbs differ also in the isotopic signature of the seep-carbonates which, overall attributable to methane oxidation, present markedly negative δ13C and positive δ18O only on the northern anticline limb. The above variability and differences are attributed to two different seepage modes which correspond also to evolutionary steps of the Salsomaggiore Ridge: a slow seepage mode that allows deposition of carbonate crusts, pods, mounds and seep-related fauna; a fast seepage mode that produce brecciated fabrics and chaotic bodies. The latter mode is considered coeval to tectonic pulses that generated the Ridge. By this integrated methodology applied to other cropping out examples in the Northern Apennines, we aim to reconstruct the complex mechanism of methane-rich fluid venting through the geological record, in particular in the Miocene
2008
- L-hand made. Educare alla cartografia. [WORKSHOP]
[Altro]
Bertacchini, Milena; Farinelli, F.; Fontana, Daniela; Garuti, N.; Maletti, M.; Marchetti, Mauro; Penon, A.; Querzé, A.; Solis, A. M.; Vianello, G.
abstract
"L-hand made, ovvero carte e paesaggi a portata di mano", è un progetto di Milena Bertacchini del Dipartimento di Scienze della Terra dell’Università di Modena e Reggio Emilia con il contributo della Fondazione Cassa di Risparmio di Modena, allo scopo di sviluppare percorsi di analisi e di scoperta delle Scienze della Terra attraverso la cartografia.La Giornata di Studi L-hand made è rivolta ad insegnanti, educatori, operatori ed interessati, per riflettere e discutere sul ruolo che la Cartografia può avere nella didattica e per presentare i risultati conseguiti dal progetto L-hand made nell'a.s. 2007-2008 in collaborazione con alcune scuole di Modena: Istituto Statale d’Arte “A. Venturi”, Liceo C. Sigonio, Liceo A. Muratori, Scuola Secondaria inferiore Guidotti, Scuola Primaria Montecuccoli (Baggiovara), Scuola Primaria C. Menotti (Villanova), Scuola Primaria G. Rodari.Collaborano al progetto: Assessorato all’Istruzione del Comune di Modena, Assessorato all’Istruzione della Provincia di Modena, Multicentro Educativo "Sergio Neri" del Comune di Modena, Servizio Accoglienza Studenti Disabili dell'Università di Modena e Reggio Emilia, Unione Italiana Ciechi, sezione di Modena.
2008
- Miocene seep-carbonates as indicators of fluid migration in northern Apennines (Italy).
[Relazione in Atti di Convegno]
Conti, Stefano; Fontana, Daniela; Mecozzi, S.; Panieri, G.
abstract
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2008
- Miocene seep-carbonates as indicators of style and intensity of fluid migration.
[Relazione in Atti di Convegno]
Mecozzi, S.; Conti, Stefano; Fontana, Daniela
abstract
Ancient hydrocarbon Miocene seep-carbonates of Miocene age have been reported from marine sedimentary successions of the northern Apennines. They are recognized by their peculiar palaeoecological, sedimentological, compositional and isotopic features as products of the microbial oxidation of methane-rich fluids and represent an excellent on-land example of carbonate bodies interpreted as the remains of ancient cold seeps. These seep-carbonates occur from internal tectonic zones (Piedmont Terziary basins, epi-Ligurian and minor basins) to external zones of the foredeep. In the Miocene foredeep, they occur crop out in large turbiditic bodies (Mt. Cervarola and Marnoso-arenacea Formations) and in slope hemipelagites (Vicchio and Verghereto Marls, and Ghioli di letto mudstones). Dominant rock types are calcilutitic/marly limestones, calcareous marls and calcarenites. Enclosing sediments are hemipelagic/turbiditic mudstones, muddy sandstones and marlstones. In the Apenninic chain, the abundance and the extent of the outcrops provide a rare opportunity to study the geometry, facies distribution and internal structures of fossil methane-derived carbonates.On the basis of morphological and stratigraphic features two main types of seep-carbonates were distinguished in the field (type 1 and 2).The type 1 is composed of a horizontal repetition of decametric to heptometric carbonate bodies, lenses and pinnacles. They have a thickness of 5 - 30 m and an extension that ranges from 10 m to 100 m. The basal portions of these huge bodies are strongly brecciated, made up of intraformational polygenic breccias and rarely extraformational. The Sasso Streghe (Modena Apennines) and Monte Petra (Romagna Apennines) carbonate outcrops are excellent examples of this type of seep-carbonates. The type 2 is made of numerous marly-calcareous lenses, irregular column-like bodies with a dimension ranging from some decimetres to 3 – 4 m and a thickness of 20- 30 cm to 3 m. Carbonate bodies are aligned along bedding strikes, or horizontally and vertically scattered and not related to a precise stratigraphic level. The Vicchio outcrops (Tuscan Apennines) are representative of this second type of carbonates. Mineralogical analyses of type 1 carbonate samples indicate that dolomite and ankerite represent the most dominant phases while Low-Mg calcite represents type 2 dominant carbonate phase. The carbon and oxygen isotopic compositions of the carbonates display very large ranges, from -10‰ to -55‰ Vienna PeeDee Belemnite (V-PDB) and from -3‰ to 6‰ V-PDB, respectively. Seep-carbonates type 1 appear significantly depleted in δ13C (ranging from -30‰ to -55‰ V-PDB) while seep-carbonates type 2 are only moderately depleted (δ13C varying from -10‰ to -23‰ V-PDB). Petrographic observations show complex facies relationships, as indicative of different stages in seep-carbonates growth.Our presentation will report the result of a detailed field observation of the two types of seep-carbonates coupled with geochemical, petrographic and mineralogical studies. In particular we discuss distinctive characters, geometry, isotope geochemistry and mineralogy, in context relationship with precipitation and recrystallisation processes of the carbonates, the origin of carbon rich fluids, and with different mechanisms of seep-carbonate formation.
2008
- Sedimentary filling of a wedge-top basin and realationship with the foredeep (Middle Miocene Marnoso-arenacea Formation, northern Apennines.
[Articolo su rivista]
Conti, Stefano; Fontana, Daniela; C. C., Lucente
abstract
The Middle Miocene Marnoso-arenacea Formation (?Langhian to Serravallian in age), at Deruta in the northern Apennines of Italy, rests unconformably on an orogenic wedge adjacent to the Adriatic foredeep. Based on a detailed facies analysis, the succession reveals two genetically related depositional systems, representing a more lower distal delta-fed sand-rich system and an upper more proximal fan-delta slope system. Petrographic data confirm the genetic relationship between the two depositional systems, with the fan-delta slope feeding the basinward sand-rich system. The Deruta depositional setting shows a multi-step sedimentary evolution controlled by tectonically induced relative sea-level changes. The first stage, corresponding to a sea-level rise, promoted deposition in a wedge-top basin of pebbly sand and sand lobes (delta-fed). The second stage, characterized by intense tectonic activity (uplift) and sea-level fall, promoted accumulation of a prograding fan-delta slope replacing the sand-rich lobes. This phase was dominated by mass failures and methanogenic cold seepages. During these stages, the wedge-top basin was isolated from the adjacent foredeep. Only during the third stage was a connection was established, with the development of a deep-sea fan in the foredeep, fed by a deltaic depositional system.
2008
- Sedimentary filling of a wedge-top basin and relationship with the foredeep (Middle Miocene Marnoso-arenacea Formation, northern Apennines)
[Articolo su rivista]
Conti, S.; Fontana, D.; Lucente, C. C.
abstract
The Middle Miocene Marnoso-arenacea Formation at Deruta in the northern Apennines of Italy rests unconformably on an orogenic wedge adjacent to the Adriatic foredeep. Based on a detailed facies analysis, the succession reveals two genetically related depositional systems: a distal delta-fed sand-rich system and a more proximal fan-delta slope system. Petrographic data confirm the genetic relationship between the two depositional systems, with the fan-delta slope feeding the basinward sand-rich system. The Deruta depositional setting shows a multi-step sedimentary evolution controlled by tectonically induced relative sea-level changes. The first stage, corresponding to a sea-level rise, promoted deposition in a wedge-top basin of pebbly sand and sand lobes (delta-fed). The second stage, characterized by intense tectonic activity (uplift) and sea-level fall, promoted accumulation of a prograding fan-delta slope replacing the sand-rich lobes. This phase was dominated by mass failures and methanogenic cold seepages. During these two stages, the wedge-top basin was isolated from the adjacent foredeep. Only during the third stage was a connection established, with the development of a deep-sea fan in the foredeep, fed by a deltaic depositional system. © Springer-Verlag 2008.
2007
- Alluvial sand composition as a tool to unravel the Late Quaternary sedimentation of the Modena Plain, northern Italy
[Capitolo/Saggio]
Lugli, Stefano; Marchetti Dori, Simona; Fontana, Daniela
abstract
The Modena alluvial plain is located on the northern side of the northern Apenninesfold-and-thrust belt, where streams draining the chain flow toward the northeastinto the Po River. The alluvial plain is characterized by a spectacular abundanceof archaeological sites of various ages and can be considered a natural laboratory forthe reconstruction of the recent sedimentary evolution of the Po Plain. Detailed modalanalyses of modern sands of the Modena Plain streams indicate that the provenancesignal can be distinguished on the basis of key components, such as quartz, feldspar,carbonate, and lithic fragments. The compositional fields of the streams depend onthe extent of the watershed, the recycling of older fluvial sediments, and the sedimentinput from tributary streams.The modal analyses demonstrate that sand composition of the major rivers (Panaroand Secchia) has not changed during the Holocene, when sediment production,storage, and dispersal were probably dominated by colluvial aggradation in an environmentcharacterized by dense vegetation cover.In the late Pleistocene, fluvial sands were characterized by higher feldspar contentscompared with modern and Holocene sands. This feldspar abundance couldreflect a high-frequency signal in sediment supply rates linked to secular variationsof weathering processes, and it reveals the strong denudation and sediment removalconditions of the last glacial stage (15–18 ka).The implication of this study is that provenance of Holocene sediments now buriedin the floodplain can be determined by a simple comparison with modern sandcomposition. Sand composition studies may represent a useful tool to reconstruct thePleistocene-Holocene fluvial sediment supply and the evolution of human settlementsas function of climate and drainage system changes.
2007
- Fluid seepage in mud volcanoes of the northern Apennines: An integrated geophysical and geological study.
[Articolo su rivista]
F., Accaino; A., Bratus; Conti, Stefano; Fontana, Daniela; U., Tinivella
abstract
An integrated geophysical and geological study of small mud volcanoes occurring along the external compressive margin of the chain in the northern Apennines has beenwas carried out in order to investigate the fluid pathways and the mud reservoir. Results obtained by tomographic inversion of first arrivals of 3D seismic data, and models obtained by 2D geo-electrical data, have permittedmade it possible to determine the geometry of the buried shallow structures, and the details of the fluid seepage until down to 50 m below the mud volcano surface.A mud chamber has beenwas identified at a depth of 25 meters. This shallow reservoir could represent the last phase of mud accumulation before the final emission.The comparison Comparison with other mud volcanoes of the northern Apennines suggests a close relationship between extruded materials and substratum typology
2007
- Gemma 1786, il Museo Mineralogico e Geologico Estense del Dipartimento di Scienze della Terra. CD-Rom multimediale-Progetto "Musei Scientifici Universitari Modenesi" a cura del Servizio Accoglienza Studenti Disabili dell’Università di Modena e Reggio Emilia
[Esposizione]
Bertacchini, Milena; Fontana, Daniela; Galli, Ermanno; Gavioli, Giovanna; Rossi, Antonio
abstract
In un CD-Rom accessibile anche a non vedenti è presentato il Museo Universitario "Gemma 1786", dalle sue origini alle più recenti attività, attraverso le collezioni ed il suo patrimonio storico-culturale. Il progetto, a cura del Servizio Accoglienza Studenti Disabili dell’Università degli Studi di Modena e Reggio Emilia (prof. Gavioli G.), coinvolge tutti e sei i Musei Universitari Modenensi per valorizzarli e promuovere una loro conoscenza anche ad un pubblico con disabilità.
2007
- Genius loci: l’anima dei luoghi ritrovati. Mostra, Museo Universitario "Gemma 1786", Dipartimento di Scienze della Terra, 6-20 maggio 2007
[Esposizione]
Bertacchini, Milena; Fontana, Daniela; Galli, Ermanno; Gavioli, Giovanna; Guaraldi, Giacomo; Padovani, Veronica; Rompianesi, P.; Rossi, Antonio; Zinanni, M.
abstract
Genius loci è l’anima dei luoghi ritrovati presentati attraverso una selezione di una trentina di immagini tratte da una raccolta fotografica composta da oltre un centinaio tra negativi e lastre eseguite da fotografi dilettanti locali sconosciuti del secolo scorso.Ogni riproduzione rappresenta un documento visivo delle trasformazioni che hanno caratterizzato il paesaggio naturale e sociale del territorio emiliano e italiano tra la fine dell’Ottocento e la prima metà del Novecento. Tra i soggetti: paesaggi urbani e appenninici, ritratti di personaggi e di gente comune, scene di vita quotidiana e di eventi catastrofici naturali.Ogni immagine esposta è un frammento della memoria locale in grado di suscitare emozioni, sentimenti e forse anche ricordi lontani in chi le osserva. Ogni fotografia fa rivivere l’anima di quel “genius loci” che ne ispirò lo scatto.Evento realizzato con il contributo della Fondazione Cassa di Risparmio di Modena in collaborazione con il Servizio Accoglienza Studenti Disabili dell'Ateneo di Modena.
2007
- I vulcani di fango dell'Appennino modenese: fenomeni attuali e fossili
[Relazione in Atti di Convegno]
Conti, Stefano; Fontana, Daniela
abstract
-
2007
- Integrated geophysical investigation of a mud-volcano in the Northern Apennines.
[Relazione in Atti di Convegno]
Bratus, A; Accaino, F; Tinivella, U; Conti, Stefano; Fontana, Daniela
abstract
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2007
- La passione di una vita. Museo Universitario "Gemma 1786", Dipartimento di Scienze della Terra, nell'ambito dell'iniziativa "Genius loci: l’anima dei luoghi ritrovati", 5 maggio 2007
[Esposizione]
Bertacchini, Milena; Fontana, Daniela; Galli, Ermanno; Rompianesi, P.; Rossi, Antonio
abstract
Incontro con il naturalista modenese Pietro Rompianesi per suscitare emozioni, ricordi, suggestioni di terre lontane, con le esperienze vissute da questo studioso e appassionato della ricerca geologica e naturalistica.
2007
- Le Salse di Nirano
[Software]
Castaldini, Doriano; Conti, Stefano; Conventi, M.; Dallai, Daniele; DEL PRETE, Carlo; Fazzini, M.; Fontana, Daniela; Gorgoni, Carlo; Ghinoi, A.; Russo, Antonio; Sala, Luigi; Serventi, Paolo; Verri, D.; Barbieri, Massimo
abstract
Questo CD-Rom, organizzato in appositi capitoli contrassegnati da colori differenti, riunisce i diversi aspetti della Riserva Naturale delle Salse di Nirano in cinque unità tematiche, alle quali è possibile accedere attraverso il menu di navigazione o attraverso un'apposita pagina introduttiva.Il primo capitolo s'intitola HOME e contiene, oltre alla pagina iniziale, i paragrafi relativi alla guida al CD-Rom, agli autori e alla mappa del sito.Il secondo, chiamato RISERVA, ha come oggetto la Riserva Naturale delle Salse di Nirano, descritta sotto il profilo storico-istituzionale, negli aspetti legati alle strutture di accoglienza e dei servizi offerti, oltre a fornire le informazioni sul regolamento di fruizione dell'area e sulle pubblicazioni inerenti le Salse di Nirano .Il terzo, ASPETTI SCIENTIFICI, raggruppa appunto gli aspetti più prettamente scientifici della riserva naturale delle Salse di Nirano, e contiene i "paragrafi" relativi alla geologia, al clima, alla geomorfologia, ai fossili, alla flora e vegetazione ed alla fauna.Il quarto capitolo, ASPETTI TURISTICI, fornisce una serie di utili informazioni turistiche ed allega una lista di interessanti attrazioni nei dintorni di Nirano; esso contiene inoltre un paragrafo dedicato alla Carta Geoturistica della Riserva.Il quinto capitolo, GALLERIA MULTIMEDIALE, contiene una ricca raccolta d'immagini delle Salse di Nirano, di suoni registrati all'interno della Riserva e di filmati delle salse; di particolare rilievo il volo virtuale sulla Riserva, un modo tutto nuovo di osservare il territorio di Nirano. La galleria multimediale presenta inoltre una significativa bibliografia scientifica sul fenomeno generale delle Salse e sui vari aspetti della riserva di Nirano, un'apposita sitografia (una raccolta di siti web) assieme ad una galleria studi in cui si possono scaricare i pdf di pubblicazioni scientifiche che permetteranno al lettore particolarmente interessato di approfondire i singoli aspetti sulle salse di Nirano.
2007
- Seep-carbonates and fluid expulsion processes in the Miocene of the northern Apennines.
[Relazione in Atti di Convegno]
Conti, Stefano; Fontana, Daniela; Mecozzi, Silvia
abstract
In the Miocene satellite and foredeep basins of the northern Apennines numerous carbonate bodies were identified by specific palaeoecological, sedimentological, compositional and isotopic features as products of the microbial oxidation of methane-rich fluids (Conti and Fontana, 1999a, 2002 and references herein).These methane-derived carbonates occur in large turbiditic bodies (Mt. Cervarola and Marnoso-arenacea Formations) and in slope hemipelagites (Vicchio and Verghereto Marls, and Ghioli di letto mudstones). Dominant rock types are calcilutitic limestones, marly limestones, calcareous marls and calcarenites. Carbonates exhibit typical 13C-depleted signatures indicative of methane oxidation On the basis of morphological and stratigraphic features two main types of seep-carbonates were distinguished in the field (Type 1 and 2 Conti and Fontana,1999a).The first type (Type 1) is composed of a horizontal repetition of decametric to heptometric carbonate bodies, lenses and pinnacles. They have a thickness of 5 - 30 m and an extension that ranges from 10 m to 100 m. The lateral contacts with marls and arenitic mudstones (host sediments) vary from sharp to transitional. The basal portions of these huge bodies are typically strongly brecciated, made up of intraformational polygenic breccias and rarely extraformational. The Sasso Streghe (Modena Apennines) and Monte Petra (Romagna Apennines) carbonate outrops are excellent examples of this type of methane-derived carbonates.The second type (Type 2) consist of numerous marly-calcareous lenses, irregular column-like bodies with a dimension that ranges from some decimetres to 3 – 4 m and a thickness of 20- 30 cm to 3 m. Carbonate Type 2 bodies can be aligned along bedding strikes or horizontally and vertically scattered and not related to a precise stratigraphic level. Many of them consist of several lenticular units vertically stacked and separated by thin pelitic levels, thus suggesting periodic growth. The Vicchio outcrops is clearly representative of this second type of carbonates.Carbon isotope measurements show that carbonates from Type 1 and 2 are tipically depleted in 13C but the amount of depletion seem to differ between them. Therefore seep-carbonates Type 1 appear significantly depleted in δ13C (up to …) while seep-carbonates Type 2 are only moderately depleted (…). Our presentation will draw attention to the distinctive characters of the two types of chemoherms, In particular we discuss geometry, isotope geochemistry and brecciation, in context with the composition and origin of carbon rich fluids, the flux discharge and rate, and with the mechanisms of expulsion (diffused or focused).
2006
- Authigenic seep-carbonates cementing coarse-grained deposits in a fan-delta depositional system (middle Miocene, Marnoso-arenacea Formation, central Italy).
[Relazione in Atti di Convegno]
Conti, Stefano; Fontana, Daniela; Gubertini, ; A., Lucente; Cc,
abstract
Outer shelf cracks and elongated gas blow out features have been first discovered along a 40 km long section of the U.S. Atlantic margin. Her, individual cracks are several km long, 1km wide and up to 50 m deep (Driscoll et al., 2000, Hill et al., 2004). The cracks and depressions seem to be caused by "gas blow outs" related to the release of shallow trapped gas. The precise age of the blowouts and the origin of the gas remains unknown, but post-LGM formation of the blowout features suggest that ocean warming triggered methane hydrate dissociation processes.The fact, that the gas hydrate outcrop zones of the largest gas hydrate provinces in Europe are on the Norwegian-Barents-Svalbard (NBS) margin makes the U.S. Atlantic margin - Norwegian Atlantic margin reaction of potential gas hydrates fields to post- Last Glacial Maximum (LGM) climate conditions particularly important for studies of submarine slope failures, i.e. geohazards. The NBS margin is not only an important gas hydrate province but also an area where numerous seeps are documented, and we thus know that there is gas migration in the sediments. In particular the area, where the theoretical outcrop zone of the base of the gas hydrate stability zone (BGHS) and the geophysical evidence as a bottom simulating reflector (BSR) lies, we observe outer shelf cracking, gas blow outs, shallow faulting and fluid escape features such as pockmarks in sediments. Our presentation will draw attention (1) to a system of cracks associated with high pockmark density "gas blowout" features along the northern extension of the giant and retrogressive Storegga slide on the Mid-Norwegian Margin and (2) to a system of potential large blowout features and shallow faults influencing slope failures on the W-Svalbard margin. On the Mid-Norwegian margin a 50 km long and up to 3 km wide zone of approx. 10 m deep depressions occur. They line up with the northern edge of the Storegga headwall elongating in N-S direction. Within the uncertainty of the BGHS modelling the approx. 50 ms TWT cracking zone corresponds well to the belt of the BGHS outcrops, where they intersect the upper continental slope. Radiocarbon age dating of the cracking reveals the same age on the main crack as the Storegga Slide event, but due to the 14C dating uncertainties it remains unknown whether the cracking predates, occurs at the same time, or postdates the Holocene giant submarine sliding event. The cracks are associated with fluid escape indicated by pockmarks typically 50-300 m in diameter and 1-5 m deep. On the W-Svalbard margin outer shelf post-LGM faulting and large depressions occur. The depressions have a diameter of 6 -10 km and a depth of up to 100 m but also smaller depressions (<20m) exist. The presented post-LGM formation of cracks, faults and gas blow out features along U.S. and Norwegian Atlantic margin outer shelf areas may be the result of a time dependent response of ocean clathrate reservoirs to climate change and therefore a "climate induced geohazard".
2006
- Fluid flow pathway and configuration of buried structures in mud volcanoes of the northern Apennines.
[Relazione in Atti di Convegno]
Accaino, F; Bratus, A; Conti, Stefano; Fontana, Daniela; Tinivella, U.
abstract
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2006
- Geophysical investigation of a mud-volcano in the Northern Apennines
[Relazione in Atti di Convegno]
Accaino, F.; Bratus, A.; Tinivella, U.; Conti, Stefano; Fontana, Daniela
abstract
In the frame of a cooperation between the Earth Science Department of the University of Modena and Reggio Emilia and the OGS
2006
- I carbonati connessi ad emissioni di fluidi ricchi in metano: i risultati di dieci anni di studi nell’Appennino settentrionale.
[Relazione in Atti di Convegno]
Conti, Stefano; Fontana, Daniela
abstract
Durante l’ultimo ventennio, l’emissioni di fluidi freddi è stata ampiamente documentata lungo i margini continentali attivi. L’espulsione dei fluidi nei prismi di accrezione è favorita dalle sovrapressioni interstiziali indotte dal carico tettonico e le velocità di emissione sono legate all’entità dei processi tettonici. Ai processi tettonici si possono sovrapporre processi climatici, ed entrambi possono contribuire a fenomeni d’instabilità sedimentaria. L’emissione di fluidi freddi è evidenziata da vari indicatori quali: - depositi di carbonati autigeni, - fuoriuscita d’idrocarburi liquidi e gassosi, - vulcani di fango e strutture legate a processi diapirici, - presenza di depositi ricchi in clatrati, - deformazioni sinsedimentarie, - presenza di peculiari comunità bentoniche chemiosintetiche. Il riconoscimento di questi caratteri è importante per identificare i processi ed i meccanismi che controllano l’espulsione dei fluidi nei margini continentali.I depositi fossili, quali quelli presenti nell’Appennino settentrionale, sono importanti perché forniscono una documentazione temporale dei processi di espulsione dei fluidi: evidenziano la struttura e l’evoluzione del sistema di circolazione dei fluidi e soprattutto i rapporti tra tettonica e sedimentazione. I depositi fossili sono riconoscibili per la presenza di: - carbonati autigeni impoveriti dell’isotopo 13C, - peculiari comunità chemiosintetiche, - strutture sedimentarie legate a processi diapirici. In quest’ultimo decennio abbiamo esaminato i carbonati legati alle emissioni di fluidi ricchi in metano in numerosi affioramenti del Miocene medio-superiore dell’Appennno Settentrionale. Questi depositi si trovano in vari contesti geotettonici della catena appenninica: nelle zone più interne si concentrano nei bacini satelliti epiliguri, (Marne del Termina del Serravalliano superiore-Tortoniano inferiore) mentre in quelle più esterne dell’avanfossa sono presenti generalmente nella parte prospiciente il fronte deformativo. In particolare, nell’avanfossa sono concentrati in due distinte posizioni: - in intervalli pelitici legati ad alti intrabacinali intercalati nella successione langhiano-serravalliana delle Formazioni del M. Cervarola e della Marnoso-arenacea, - in emipelagiti di scarpata di età compresa tra il Serravalliano ed il Messiniano inferiore (Marne di Vicchio, Marne di Verghereto e marne di letto) che delimitano al tetto le sopra citate formazioni. In quest’ultima situazione, i carbonati autigeni sono situati poco al di sotto del contatto tettonico con le unità Liguri.I carbonati sono irregolarmente distribuiti nel sedimento in senso sia orizzontale che verticale; pur non essendo degli indicatori stratigrafici, si concentrano solo in particolari momenti della successione stratigrafica miocenica. Morfologia e litologia dei corpi cartonatici sono varie, come pure le facies presenti, caratterizzate da contatti complessi. I carbonati sono associati a sedimenti di prodelta, a facies di scarpata, e soprattutto a depositi torbiditici di piana bacinale.I carbonati sono prevalentemente inclusi in sedimenti pelitici, ma possono cementare o incrostare arenarie grossolane e conglomerati. Sono sia in posizione primaria che secondaria, per rimaneggiamenti intraformazionali.Al loro interno sono state riconosciute diverse facies, alcune ricorrenti e indicative di processi di tipo diapirico. Evidenze diapiriche sono rappresentate dalla mescolanza e rimaneggiamento di sedimenti e fossili di natura molto diversa, provenienti dalle rocce incassanti, dalle chemioerme stesse, e da sedimenti extraformazionali costituiti da olistostromi. Il regime e la tipologia delle emissioni dei fluidi varia, con evoluzioni da flussi concentrati a diffusi, da esplosivi a moderati e viceversa. Le emissioni lente e moderate sono responsabili della precipitazione di grandi spessori di carbonati autigeni, con sviluppo di facies micritiche riccamente fossilifer
2006
- Palaeogeography of the Upper Cretaceous-Eocene carbonate turbidites of the Northern Apennines from provenance studies
[Relazione in Atti di Convegno]
Argnani, A.; Fontana, Daniela; Stefani, C.; Zuffa, G. G.
abstract
The Upper Cretaceous Helminthoid Flysch (HF) of the northern Apennines are thick and regionally widespread deep-water carbonate turbidite successions, deposited during the initial stages of Alpine collision. The HF span from Campanian to Early Eocene in age and are mainly composed of intrabasinal carbonate ooze mixed with clay; siliciclastic terrigenous beds are also present, but they are a volumetrically minor component of the succesion. Petrographic signatures indicate that HF were deposited in distinct basins located below the carbonate compensation depth, probably corresponded to confined sectors of oceanic floor bounded by transform fault walls. Multiple sources of detritus controlled the basin-fill of the HF, in particular: a) major intrabasinal sources from outer shelf/slope areas and pelagic plateaus which supplied coeval carbonate, mainly fine-grained sediment of biogenic origin; b) minor siliciclastic terrigenous sources from hinterland rock units (crystalline basement plus minor sedimentary covers). Bulk composition and heavy minerals of terrigenous mode indicate provenance from different crustal levels of the European and Adria plates. These data allow to place the Helminthoid Flysch units within a Late Cretaceous palaeogeographic reconstruction of the Northern Apennine Tethys. The depositional characters of these turbidites indicate the coexistence of an active tectonic setting, a palaeogeographic location prone to carbonate ooze production and storage, and limited terrigenous sources outside the basin. Palaeotectonic reconstructions and stratigraphic data suggest that Adria represented a vast repository of penecontemporaneous carbonate mud; the presumably intense seismic activity related to the pre-collisional Alpine orogeny promoted large-scale failures of shelf/slope biogenic muddy sediments, resulting in the deposition of large volume of carbonate turbidites. Only occasionally, terrigenous turbidite currents, probably linked to exceptional fluvial floods, generated pure terrigenous beds with different petrographic signatures. The small amounts of extrabasinal siliciclastic materials entering the basin, compared to the dominant intrabasinal carbonates, indicates a limited availability of sediment sources outside the basin.
2006
- Risalita di fluidi freddi ricchi in metano, carbonati autigeni ed instabilità sedimentaria nel Miocene medio-superiore dell’Appennino settentrionale.
[Monografia/Trattato scientifico]
Conti, Stefano; Fontana, Daniela; MARCHETTI DORI, S.
abstract
Negli ultimi decenni numerose ricerche hanno evidenziato che le risalite di fluidi sui fondali oceanici, sia calde che fredde, sono fenomeni globalmente estesi, con importanti implicazioni geologiche e biologiche. La risalita di fluidi è generalmente connessa con: a) precipitazione di minerali autigeni fra cui carbonati primari (calcite, aragonite e dolomite), solfuri e solfati; b) peculiari caratteristiche geochimiche dei sedimenti, delle rocce, dell’acqua e degli organismi; c) l’instaurarsi di relazioni simbiotiche fra comunità macrofaunali e microrganismi; d) la formazione di processi diapirici con caoticizzazione dei sedimenti incassanti; e) processi d’instabilità sedimentaria (frane sottomarine di varia tipologia).Verso la fine degli anni ‘70 lo studio dei fondali oceanici, con l’impulso prodotto dall’utilizzo di sottomarini, ha permesso la scoperta dell’esistenza di risalite di fluidi idrotermali arricchiti in solfuri (hot vents) caratterizzati dalla strutturazione di camini costituiti principalmente da solfuri e dalla presenza di una peculiare ed abbondante fauna chemiosintetica (Lonsdale, 1977).A partire dagli anni ‘80, il proseguire delle indagini sottomarine ha evidenziato l’esistenza di risalite localizzate di fluidi freddi ricchi in idrocarburi leggeri (cold seeps), diffusi praticamente in tutti i contesti geodinamici oceanici: nei margini attivi sono segnalati nel prisma di accrezione dell’Oregon (Ritger et al., 1987; Bohrmann et al., 1998), del Giappone (Sakai et al, 1992), del Makran (Von Rad et al, 1996), del Perù (Sample, 1996), di Barbados (Lance et al, 1998), delle Aleutine (Suess et al, 1999) e del Mediterraneo orientale (Aloisi et al, 2000), nel Mar Nero (Peckmann et al., 2001), nel mare marginale di Okhotsk (Esikov and Pashkina, 1990; Greinert, 1999), nel bacino di avanarco della Sonda (Wiedicke et al, 2002), nella scarpata continentale della Nuova Zelanda (Lewis & Marshall, 1996). Nei margini passivi sono frequenti nel Mare del Nord (Hovland et al., 1987), al largo della Danimarca (Jorgensen, 1992), alla base della scarpata a gradoni della Florida (Paull et al., 1995), nel Golfo del Messico (Roberts, 2001). Sono presenti infine nei margini trascorrenti-conservativi della California (Embley et al, 1990; Stakes et al, 1999).Come già osservato per gli hot vents, i cold seeps sono caratterizzati dalla presenza di una fauna bentonica rigogliosa, sostenuta su base chemiosintetica. Si formano comunità a bivalvi in endosimbiosi con batteri solfo-ossidanti, solfato-riducenti e metano-ossidanti (Van Dover, 2000). I batteri utilizzano energia chimica al posto della luce solare e trasformano composti inorganici in sostanze utilizzabili dai bivalvi; viceversa questi ultimi forniscono protezione ai batteri. In corrispondenza dei cold seeps si può realizzare la precipitazione di carbonati autigeni, che sono stati riconosciuti nel record geologico a partire almeno del Fanerozoico (Barbieri et al. 2001; Campbell et al, 2002, Campbell, 2006 e riferimenti bibliografici in essi contenuti). E’ ampiamente riconosciuto che i migliori indicatori di prodotti fossili di cold seeps sono: a) forte impoverimento in 13C dei carbonati, con conseguenti valori isotopici negativi del δ13C; b) associazioni di macrofauna particolare e oligotipica; c) biomarkers specifici (Campbell and Bottjer, 1993; Aharon et al, 1992; Aharon, 2000; Taviani, 2001; Peckmann et al, 2001, 2002; Campbell et al, 2002); d) peculiari strutture riconducibili a fenomeni diapirici.Interessanti esempi fossili di cold seeps sono rappresentati dal “calcare a Lucina” dell’Appennino settentrionale, oggetto della presente escursione. Questi carbonati, caratterizzati da una composizione isotopica negativa del carbonio e da una consistente presenza di fossili di bivalvi (principalmente lucinidi di grandi dimensioni), sono testimonianza di una lunga e complessa storia di risalita di fluidi arricchiti in metano perdurata dura
2006
- Sulle tracce del sale. Mostra, approfondimenti scientifici, conversazioni informali e assaggi. Museo Universitario "Gemma 1786", Dipartimento di Scienze della Terra, maggio-giugno 2006
[Esposizione]
Bertacchini, Milena; Berselli, E.; Caselli, A.; Coltellacci, Marco Maria; Fontana, Daniela; Galli, Ermanno; Lo Russo, G.; Lugli, Stefano; Pattuzzi, Edda; Rossi, Antonio; Vasta, M.; Zinanni, M.
abstract
Il sale è il filo conduttore dell’iniziativa all'insegna dell'intrattenimento e della conoscenza organizzata dal Museo Universitario "Gemma 1786" con il contributo della Fondazione Cassa di Risparmio di Modena nell’ambito della rassegna “Musei da gustare 2006” della Provincia di Modena.Scopo dell’evento è quello di invitare il pubblico a viaggiare nello spazio e nel tempo seguendo “Le tracce del sale” attraverso proposte divulgative diversificate nell'approccio e nei contenuti. PERCORSO ESPOSITIVO di campioni, prodotti e oggetti legati alla cultura del sale, illustrati da pannelli esplicativi e filmati sulla produzione del sale italiana e francese (Saline di Cervia e di Guérande). SAPIDO O INSIPIDO?, conversazioni sul tema per raccontare curiosità, segreti e verità sul ruolo del sale in cucina, sull’uso e abuso del sale, sulla sua recente riscoperta e valorizzazione, con EDMONDO BERSELLI, editorialista di La Repubblica e l’Espresso, GIUSEPPE LO RUSSO, scrittore d’enogastronomia e ricercatore di storia dell’alimentazione; ENRICO BELGRADO, storico; MARCO VASTA, fotografo-documentarista dell’Associazione onlus AàZ Aiuto allo Zanskar; GARDINI FABIO, L’Artigiano di Forlì, produttore del cioccolato con il sale di Romagna; GUIDETTI CLAUDIO, segretario sez. Modena Consorzio del Parmigiano Reggiano. INCONTRI SCIENTIFICI con esperti dell’ITALKALI SpA Palermo per illustrare le tappe che questo bene prezioso segue per arrivare alle nostre tavole; SUGGESTIONI DI SALE, installazioni di arte contemporanea ed esercizi di stile realizzati da studenti ed insegnanti dell'Istituto Statale d'Arte "Adolfo Venturi" di Modena.In collaborazione con: Cavalli-Deposito Fiscale Tabacchi Modena, Consorzio del Parmigiano Reggiano, Consorzio del Prosciutto di Modena, Consorzio Marchio Storico dei Lambruschi Modenesi, Gruppo Culturale Civiltà Salinara Cervia, HERA-META Modena, ITALKALI Società Italiana sali alcalini Palermo, SPEL Modena.Programma delle giornateSABATO 27 maggioore 10,30 “Dai giacimenti alle tavole” e “Sai quale sale mangi?”ore 18 “Sapido o insipido?” Viaggiare nella memoria di Modena e, analizzando fatti e persone del quotidiano di ieri, arrivare ad una lettura del quotidiano di oggi:OSPITI: Edmondo Berselli, Enrico Belgrado, Giuseppe Lo Russo, Claudio Guidetti, Fabio Gardini.DOMENICA 28 maggioore 10,30 “Sai quale sale mangi?”ore 18 “Sapido o insipido?” Viaggiare nello spazio alla scoperta dell’oro bianco in altri continenti: “Le carovane di sale in Himalaya”OSPITI: Marco Vasta, Milena Bertacchini, Stefano Lugli.Assaggi e degustazioni di sapori lontani salati e non.
2005
- Anatomy of seep-carbonates: ancient examples from the Miocene of the northern Apennines (Italy)
[Articolo su rivista]
Conti, Stefano; Fontana, Daniela
abstract
Ancient hydrocarbon seep-carbonates of Miocene age have been reported from marine sedimentary successions of the northern Apennines in the form of irregularly shaped micritic masses containing abundant fossil remains of oligotypic assemblages. They are recognized by their peculiar biological, sedimentological and geochemical features, and represent an excellent on-land example of carbonate bodies interpreted as the remains of ancient cold seeps. In the Apenninic chain, the abundance and the extent of the outcrops provide a rare opportunity to study the geometry, facies distribution and internal structures of fossil methane-derived carbonates. The present study reports an integrated view of the sedimentology, mineral paragenesis and geochemistry of these seep-carbonates in two different tectono-sedimentary settings: foredeep and satellite basins. The main result of this study is the recognition of 17 facies in the investigated seep-carbonates. The detailed facies and microfacies analysis led to the identification of different structures, which occur in well-defined parts of the carbonate masses. The recurring and broadly similar stratigraphy and facies association from the two considered geological environments is diagnostic of the different stages of seep-carbonate formation and evolution.
2005
- Brecciated lithofacies in methane-derived carbonates in Middle-Late Miocene deposits (Northern Apennines, Italy).
[Relazione in Atti di Convegno]
Gubertini, A; Conti, Stefano; Fontana, Daniela
abstract
More than one hundread occurrences of methane-derived carbonate rocks cropping out in Middle-Late Miocene satellite and foredeep basins of the northern Apennines (pelitic intervals of the Mt. Cervarola and Marnoso-arenacea Formations and slope/closure hemipelagites) have been investigated. These authigenic carbonate blocks are interpreted as fossil equivalents of modern carbonate crusts, slabs or chimneys precipitated at cold seeps.We analyzed stratigraphical, compositional and geochemical aspects of brecciated lithofacies that characterize large portions of carbonate bodies, in order to reconstruct different phases of fluid venting and precipitation of authigenic phases.Apennine seep carbonates include two main types of brecciation: monogenic breccias, made up of micritic angular clasts cemented by sparry calcite or aragonite, and polygenic breccias, made up of extrabasinal and intrabasinal clasts chaotically floating in the authigenic micritic matrix.Detailed petrographic study, including UV fluorescence microscopy and cathodoluminoscope, show different typologies and distribution of mineral components, microfacies and microstructures.Mineral components of carbonates blocks are made of authigenic phases and detrital components. Authigenic minerals include micro- to cryptocrystalline micrite and sparry calcite, aragonite, pyrite, quartz and feldspars. Detrital components consist of siliciclastic, silt-sand sized terrigenous particles, fragmented macrofossils and planktonic foraminifera. Ultra-violet fluorescence microscopy shows the presence of several hydrocarbon inclusions in sparry calcite.Various microfacies are frequently intertwined and chaotically mixed. Biomicrite, pelmicrite, clotted micrite and hybrid arenites are the most common. Clotted micrite consists of dark-brown to black, cloudy aggregates rimmed by calcitic spar. Common microstructures are: veins, occluded by multiple generations of carbonate cements and/or sediment grains, corrosion surfaces, burrows, geopetal fabrics and cavities, and preferential orientation of clastic and bioclastic particles.All carbonate phases reveal strongly negative carbon isotope values (ranging from -56,25 ‰ to -10,72 ‰ vs PDB) and reflect different rate of methane oxidation, as well as variability of bacterial communities which induce carbonate precipitation. Oxygen isotope values range from -9,71 3 to +3,55 ‰ vs PDB; the positive values are concentrated in polygenic breccias.On the base of isotopic and thermometric data, the genesis of polygenic breccia can be probably related to gas hydrates dissociation. In present-day continental margins, this dissociation can trigger a widespread and intense sediment instability. The frequent association of polygenic breccias in methane-derived carbonates and chaotic deposits, could be a further evidence of gas-hydrate dissociation and fluid expulsion, and may represent the fossil activity of pseudodiapirs and/or mud volcanoes.
2005
- Composizione dei sedimenti sabbiosi nelle perforazioni lungo il tracciato ferroviario ad alta velocità: indicazioni preliminari sull'evoluzione sedimentaria della media pianura modenese
[Articolo su rivista]
Lugli, Stefano; MARCHETTI DORI, Simona; Fontana, Daniela; Panini, Filippo
abstract
The Modena alluvial plain has been geologically investigated in great detail and is characterized by a spectacular abundance of archaeological sites of various age. For this reasons the area may be considered a natural laboratory for the reconstruction of the recent sedimentary evolution of the Po Plain. The alluvial plain area examined for this study has an approximate extent of 150 km2 and is located at the northern side of the Northern Apennines thrust- and fold-belt, where streams draining the chain flow toward the north-east into the Po river. Detailed modal analyses by point-counting of thin sections show that modern stream sands in the Modena plain show similar overall compositional fields, but can be discriminated on the base of key-components, such as quartz, feldspar, carbonate and lithic fragments. The study of sand sediments indicates that the compositional fields have not varied significantly since the Neolithic. The only major diagenetic process is the formation of carbonate concretions (caliche), which can be easily recognized as secondary particles during point counting of thin sections. These results indicate that the reconstruction of the recent evolution of the local drainage system is possible by comparing ancient with modern fluvial sand compositions.The drilling of numerous wells along the new high speed train tract (TAV) provided us with new insight on the sedimentary evolution of the plain through time. The samples recovered from 6 wells reaching depths up to -50 m show that the sand sediments older than 10-12 kyr, have a significant shift in composition from the modern ones. This compositional change consists in a marked overall increase of quartz and feldspar components. The compositional variations can be explained by the combination of various factors: a) significant change in the bedrock lithology through time induced by tectonics and/or change in the local drainage pattern, and b) recycling of older fluvial sediments enriched in feldspar. Because the sands older than 10-12 kyr compared to the overlaying olocenic and modern sediments are enriched in feldspar, which is considered a particularly alterable component, the compositional differentiation can not be related to effects induced to glacial-interglacial climate changes and post-depositional diagenetic processes.The considerable change in sand composition and the stratigraphy of the deposits suggest dramatic geographical, environmental and depositional variations supporting the observation that a regional unconformity separates the Late Pleistocene from the Olocene sediments.
2005
- High resolution geophysical data in areas with evidences of fossil and active fluid seepage (Northern Apennines, Italy).
[Relazione in Atti di Convegno]
Accaino, F; Tinivella, U; DEL NEGRO, E; Bratus, A; Baradello, L; NIETO YABAR, D; Fontana, Daniela; Conti, Stefano
abstract
The University of Modena and Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS) collaborated to acquire two geophysical data set in two areas located near Sassuolo (Modena; Northen Appenines). The first area is characterized by fossil fluid expulsion structures forming in the Upper Miocene, while the second one is actually interested by expulsion of mud and free gas. We used seismic 3D surveys to reconstruct in detail the shallow structures in both areas. Ground Penetrating Radar (GPR) and geo-electrical survey are used only in the second area to better characterize the first meters. The fossil structures located in the first area (Sasso Strega) have a horizontal dimension of about 10 meters, and a vertical extension of few ten. To investigate the presence of these buried structures a 3D seismic acquisition was performed, in which additional shots are located across the investigated area by using the natural topography to have the same effect of a deep source. In this way, the structures are lightened directly from the bottom. The source was the mini-bang and the receivers are vertical geophones (10 Hz). The receiver inline and cross-line intervals were 5 m, while the source interval was equal to 5 m (for inline shots) and 10 m (for cross-line shots). After the processing of the data to increase the signal/noise ratio, the tomographic inversion of the first breaks was applied to determine the geometry and the compressional velocity of buried structures. In the second site (near Nirano), a 3D seismic acquisition was acquired using three component geophones. In this case, the source was a Vibroseis source, that generates both compressional and shear waves. So, the acquisition allowed us to obtain information about both compressional and shear velocity fields by using the inversion tomography of the first arrivals. Of course, the comparison between the two fields is an useful tool to investigate the fluid presence in the investigated area. In fact, it is well known that the compressional velocities are influenced by both matrix and fluid, while the shear velocities detect only the matrix change.In this site we also collected geoelectrical and GPR data to recostruct the shallow features of the subsoil. In particular the geoelectrical data are inverted using tomographic approach to obtain the resistivity and chargeability models.We present the preliminary results of the collected data in the two areas.
2005
- La Cartografia nei suoi molteplici aspetti, reali ed immaginari. 8 aprile-21 maggio 2005. Mostra in occasione della riapertura al pubblico del Museo Universitario del Dipartimento di Scienze della Terra "Gemma 1786"
[Esposizione]
Bertacchini, Milena; Fontana, Daniela; Baldelli, F.; Valbonesi, G.
abstract
La riapertura al pubblico del Museo Universitario del Dipartimento di Scienze della Terra, rinominato "Gemma 1786", è stata un'occasione per presentare al pubblico in una veste rinnovata le collezioni museali di minerali, rocce e carte.Le carte sono espressione dell'uomo e della sua necessità di conoscere il territorio in cui vive. Le carte raccontano quindi dell'uomo e del territorio.La mostra, realizzata in collaborazione con l'Archivio Storico del Comune di Modena e la Biblioteca d'Arte L. Poletti di Modena, ha voluto mettere a confronto rappresentazione cartografiche antiche e recenti del territorio modenese con rivisitazioni artistiche dell'artista Giovanni Valbonesi realizzate con tecniche a collage.
2005
- La nuova sezione museale di cartografia. Inaugurazione. Museo Universitario del Dipartimento di Scienze della Terra "Gemma 1786", riapertura al pubblico, 8 aprile 2005.
[Esposizione]
Bertacchini, Milena; Fontana, Daniela
abstract
La riapertura al pubblico del Museo Universitario del Dipartimento di Scienze della Terra, rinominato "Gemma 1786", è stata un'occasione per presentare al pubblico in una veste rinnovata le collezioni museali di minerali, rocce e carte. La sezione cartografica, che si compone di un’importante raccolta di plastici cartografici ottocenteschi a colori di pregevole fattura e di numerose carte storiche e recenti, topografiche e tematiche, del territorio locale, nazionale ed estero; è stata valorizzata nella sua esposizione ed ampliata e corredata di una serie di pannelli esplicativi di valore informativo e didattico, illustranti i principi generali della cartografia e le nuove frontiere di questa disciplina.
2005
- Looking for evidence of the past presence of gas hydrates in ancient sedimentary successions.
[Relazione in Atti di Convegno]
Clari, P; Cavagna, S; DELA PIERRE, F; Martire, L; Fontana, Daniela; Conti, Stefano
abstract
The present-day distribution of gas hydrates is world-wide, in permafrost of polar regions and along outer continental margins, and they are one of the more “hot” topics of modern geo-marine research. In fact, not only GH are considered by industry as a viable energy source for the future, but their possible involvement in margin stability and climate change attracts the interest of all researchers.In order to assess the real relevance of GH dissociation on both margin stability and climate changes, it could be useful to look into the sedimentary record for possible evidence both of mass wasting processes due to GH dissociation and of past, global peaks of GH dissociation. To do that, specific evidence of the occurrence of ephemeral products such as GH in ancient sedimentary sequences are needed. The presence of gas in sediments can leave “solid" evidence as authigenic carbonates generated by aerobic or anaerobic degradation of methane. “Cold seep carbonates” can be considered the specific proxy needed to identify sedimentary sequences flushed by CH4 rich fluids, bearing, however, in mind that not all the gas-charged fluids circulating in the sedimentary column originate from the dissociation of GH . Also the presence of brecciated structures, chaoticization of sediments by soft-sediment deformations and mud diapirism, have been considered as a convincing evidence of the past presence of GH as such features are widespread in the sediments hosting GH along present-day continental margins.Two possible lines of evidence can so be suggested to assess the past presence of GH in ancient sedimentary sequences:1)The presence of carbonate rocks resulting from diagenetic processes linked to biological degradation of gas previously trapped as GH. 2)The chaoticization of sediments generated by the large changes in pore fluid volumes due GH formation and dissociation. As a whole, lithological products of the dissociation of GH are , recently named clathrites. 3)Petrological, mineralogical and geochemical characteristics of clathrites are still imperfectly known as very few examples of present-day carbonate rocks precipitated within or in proximity to gas hydrate have been described. In ancient sediments, clathrites are concealed by other types of cold seep carbonate rocks that share with them an origin due to bacterial degradation of methane. The question is: how is possible to evaluate if that particular methane was caged in the gas hydrate structure before reaching the site where it was degraded by bacteria triggering carbonate precipitation? Methane-derived carbonate preserve the geochemical signatures of the interstitial fluids from which they are derived, registering not only the involvement of methane in their formation, but also, within certain limits, the oxygen isotopic signature of the water in which they formed. During hydrate formation, water molecules containing the 18O isotope are preferentially incorporated in the hydrate structure leaving the residual brines enriched in the light 16O isotope. The reverse happens during hydrate dissociation when an input of gas-driven,18O- enriched water, flushes the surrounding sediments. The carbonate phases resulting from the bacterial degradation of methane are so viable to register these changes in isotopic composition of pore-waters and to preserve it in the sedimentary record.However, as the oxygen isotopic composition of pore waters is influenced also by other factors unrelated to the presence of hydrates (evaporation, temperature, clay-dehydration) it is not correct at the moment to identify a clathrite only on the basis of its oxygen isotope composition. Only if the stratigraphic and structural setting of the carbonates are perfectly known and additional evidence as mineralogical composition, petrological features (as fluid inclusion) and chaotic structures of the enclosed sediments are present, the definition of a seep-carbonate as a clathrite can be proposed.
2004
- A multidisciplinary study of middle Miocene seep-carbonates from the northern Apennine foredeep (Italy)
[Articolo su rivista]
Conti, Stefano; Fontana, Daniela; A., Gubertini; Sighinolfi, Giampaolo; F., Tateo; Fioroni, Chiara; Fregni, Paola
abstract
Several pelitic intervals are intercalated at various levels within the marly-arenaceous turbiditic successions of the middle Miocene northern Apennine foredeep. They range in thickness from 30 to 200 m, and represent sedimentation on top of ephemeral structural highs related to blind faults. Sediments are made up of hemipelagites and fine-grained turbidites, and include C-13-depleted carbonates, related to the rising of methane-rich fluids (hydrocarbon seep-carbonates). Large portions of pelitic intervals are involved in chaotic masses by soft sediment deformation (slumps, slides, intraformational breccias), revealing an intense sediment instability during middle Miocene. A stratigraphic, mineralogic and geochemical study was conducted on two of these pelitic intervals (Castagno d´Andrea, Mt Citerna) in order to reconstruct carbonate development, the composition of fluids, and to document the connections between fluid seepage and syndepositional tectonics. This multidisciplinary approach has allowed us to discriminate between the two examined pelitic intervals in terms of age, depositional rates and conditions, organic carbon and post-depositional processes. Seep-carbonates are characterized by chemosymbiotic fossil communities, autoclastic fractures and brecciation; carbonate bodies show complex facies relationships, as indicative of different stages in chemoherm growth. The compositional study evidences the peculiar chemistry of chemoherm carbonates (calcite low in Mg and Sr) compared with carbonates in associated enclosing pelites and with modern chemoherms, in general. The non-carbonate components within the chemoherms are enriched in detrital minerals and depleted in phyllosilicates with respect to the enclosing pelites. The mineralogical changes in the clay component within the brecciated unit of the Castagno d´Andrea chemoherms suggest authigenic precipitation of the Mg-rich phases. Isotopic analyses show the distinct carbon signature in the chemoherms from the two examined intervals (Castagno d´Andrea chemoherms more depleted, from - 15.8parts per thousand up to - 41.3parts per thousand PDB, than Mt Citema, from - 5.2parts per thousand up to - 16.7parts per thousand), and the transitional C-13-depletion trend observed moving from chemoherms to the enclosing pelites (moderately depleted) and Te (Bouma sequence) turbidites (in the range of marine carbonates). A slight but significant enrichment in delta(18)O (up to +1.4% PDB);is observed for all chemoherms when compared to values of carbonate phases present in enclosing pelites. Geochemical data indicate that the brecciated facies of seep-carbonates are related to an explosive release of gaseous fluids probably associated with the rise of deep hypersaline fluids.
2004
- Composition of sands in cores along the high-speed rail (TAV): Preliminary indications on the sedimentary evolution of the Modena plain
[Articolo su rivista]
Lugli, S.; Dori, S. M.; Fontana, D.; Panini, F.
abstract
The Modena alluvial plain has been geologically investigated in great detail and is characterized by a spectacular abundance of archaeological sites of various age. For this reasons the area may be considered a natural laboratory for the reconstruction of the recent sedimentary evolution of the Po Plain. The alluvial plain area examined for this study has an approximate extent of 150 km2 and is located at the northern side of the Northern Apennines thrust- and fold-belt, where streams draining the chain flow toward the northeast into the Po river. Detailed modal analyses by point-counting of thin sections show that modern stream sands in the Modena plain show similar overall compositional fields, but can be discriminated on the base of key-components, such as quartz, feldspar, carbonate and lithic fragments. The study of sand sediments indicates that the compositional fields have not varied significantly since the Neolithic. The only major diagenetic process is the formation of carbonate concretions (caliche), which can be easily recognized as secondary particles during point counting of thin sections. These results indicate that the reconstruction of the recent evolution of the local drainage system is possible by comparing ancient with modern fluvial sand compositions. The drilling of numerous wells along the new high speed train tract (TAV) provided us with new insight on the sedimentary evolution of the plain through time. The samples recovered from 6 wells reaching depths up to -50 m show that the sand sediments older than 10-12 kyr, have a significant shift in composition from the modern ones. This compositional change consists in a marked overall increase of quartz and feldspar components. The compositional variations can be explained by the combination of various factors: a) significant change in the bedrock lithology through time induced by tectonics and/or change in the local drainage pattern, and b) recycling of older fluvial sediments enriched in feldspar. Because the sands older than 10-12 kyr compared to the overlaying olocenic and modern sediments are enriched in feldspar, which is considered a particularly alterable component, the compositional differentiation can be related to effects induced to glacial-interglacial climate changes but not to post-depositional diagenetic processes. The considerable change in sand composition and the stratigraphy of the deposits suggest dramatic geographical, environmental and depositional variations supporting the observation that a regional unconformity separates the Late Pleistocene from the Olocene sediments.
2004
- Composizione dei sedimenti sabbiosi nelle perforazioni lungo il tracciato ferroviario ad Alta Velocità: indicazioni preliminari sull’evoluzione sedimentaria della media pianura modenese.
[Relazione in Atti di Convegno]
Lugli, Stefano; MARCHETTI DORI, Simona; Fontana, Daniela; Panini, Filippo
abstract
-
2004
- Deep-sea fluid expulsion and related products in the Miocene foredeep and satellite basins of the northern Apennines, Italy.
[Articolo su rivista]
Clari, P; Conti, Stefano; Fontana, Daniela; Taviani, M.
abstract
The last two decades have convincingly documented that both hot and cold fluid expulsion on the deep seafloor is a widespread, almost cosmopolitan phenomenon whose hydrological, geological and biological implications are multifold. Defluidization has been shown to be conducive to: (i) precipitating a variety of authigenic minerale, primarily carbonates (calcite, aragonite, dolomite), sulfides and sulphates; (ii) imposing distinct chemical signatures in sediments, rocks, biota and water; (iii) sustaining peculiar microbial consortia and macrofaunal communities. Beginning with the mid-80’s submarine investigations revealed the presence of localized deep-sea seeping of light hydrocabon-rich fluids (cold seeps) in many different geodynamic settings of the World’s oceans (e.g., Paull et al., 1984, 1992; Kulm et al., 1986; Aharon and Sen Gupta, 1994; Aharon, 2000; Bohrmann et al., 1998, 2002). As observed earlier at hydrotermal vent sites, modern loci of hydrocarbons-rich fluid seepage are characterized by a significantly high benthic biomass represented by microbial consortia and chemosynthetic macro-assemblages typically dominated by endosymbiont-bearing bivalves including clams (lucinaceans, Solemya, vesicomyids etc.), modiolid mussels (e.g., Bathymodiolus, Modiolus) as well as gastropods (e.g., Thalassonerita, Provanna), and tube worms (Pogonophora). These communities, in analogy with those found around hydrothermal vents, are basically sustained by a chemosynthetic food chain exploiting the bacterial oxidation of methane and/or hydrogen sulfide (Van Dover, 2000, with references therein.). Cold seepage may promote the formation of authigenic carbonates which can be recognized in the geological legacy of the Earth since the Phanerozoic and possibly earlier (Barbieri et al., 2001; Campbell et al., 2002).
2004
- Fluid expulsion imprints in sedimentary chaotic intervals of the northern Apennines; seep-carbonates from the Miocene foredeep and satellite basins.
[Relazione in Atti di Convegno]
Conti, Stefano; Fontana, Daniela; Gubertini, A.
abstract
Seep-carbonates are considered one of the most reliable indicators of fluid–expulsion processes along convergent margins.The majority of identified carbonate deposits containing fossil chemosynthetic assemblages (seep-carbonates) in the northern Apennines are concentrated in middle-late Miocene pelitic successions from two distint basin types: internal satellite Epiligurian basins, and external foredeep. The Epiligurian sediments consist of various depositional sequences; seep-carbonates are located in the middle-late Miocene outer shelf-slope deposits. In the foredeep, they occur in marly and clayey hemipelagites and fine-grained turbidites, located in slope-closure deposits (Langhian-early Messinian in age) passing laterally and capping huge arenaceous turbidites, or in slope deposits draping ephemeral topographic highs intercalated within the Langhian-early Serravallian basin plain turbidites (Mt Cervarola and Marnoso-arenacea Fms). In satellite basins, seep-carbonates occur in primary position and are associated with large debris flow deposits, whereas in the foredeep they are mainly hosted in thick pelitic intervals affected by an intense sediment instability such as slumps, intraformational breccias and extraformational slides.The great variability of the Apennine tectonic settings permitted different mechanisms of fluid expulsion: from diffuse discharge of pore fluids, related to mud diapir processes, to focussed or structurally aligned, fault-controlled pore fluid expulsion. Evidence of widespread discharge of fluids is commonly found in the chemoherms located in shallow-water deposits of the satellite basins and in foredeep slope pelites. Fault-controlled fluid expulsion characterizes venting within the thick pelitic intervals intercalated in the turbidite foredeep successions.These differences can be related to the degree of tectonic loading and rate of defluidization between the geometrically more elevated Epiligurian basins and the foredeep basins. Moreover, possible gas-hydrate contributions to fluid-expulsion processes are hypothesized in the foredeep, due to the more favorable conditions for gas hydrate dissociation in with respect to satellite basins
2004
- Late Cretaceous carbonate turbidites of the Northern Apennines: Shaking Adria at the onset of Alpine collision
[Articolo su rivista]
Argnani, A.; Fontana, Daniela; Stefani, C.; Zuffa, G. G.
abstract
Thick and regionally widespread deepwater carbonate turbidite successions, the Upper Cretaceous Helminthoid Flysch, were deposited during the initial stages of Alpine collision. Despite the dominant intrabasinal origin, bulk composition and heavy minerals of minor terrigenous mode indicate provenance from different crustal levels of the European and Adria plates. These data allow us to place the Helminthoid Flysch units within a Late Cretaceous paleogeographic reconstruction of the Northern Apennine Tethys. The depositional characters of these turbidites indicate the coexistence of an active tectonic setting, a paleogeographic location prone to carbonate ooze production and storage, and limited terrigenous sources outside the basin.
2004
- Le litofacies brecciate in calcari metano-derivati dell’Appennino settentrionale (Miocene medio-superiore): caratteri composizionali e geochimici.
[Relazione in Atti di Convegno]
Gubertini, A.; Fontana, Daniela
abstract
-
2004
- Reconstructing the sedimentation history of an alluvial plain by sand composition investigations: the Modena case study
[Relazione in Atti di Convegno]
Lugli, Stefano; MARCHETTI DORI, Simona; Fontana, Daniela
abstract
The Modena alluvial plain area examined for this study has an approximate extent of 150 km2 and is located at the northern side of the Northern Apennines thrust- and fold-belt, where streams draining the chain flow toward the north-east into the Po river. Detailed modal analyses by point-counting in thin sections show that modern stream sands in the Modena plain show similar overall compositional fields, but can be discriminated on the base of key-components, such as quartz, feldspar, carbonate and ophiolitic fragments.The spectacular abundance of archaeological sites of various age along the main rivers allowed us to reconstruct the variation through time of the sand composition. The study of sand sediments that buried Neolithic, Iron Age, Bronze Age, Roman and Longobardian sites indicates that the compositional fields have not varied significantly since the Neolithic. These results clearly indicate that the bedrock lithology of the source area has not changed in the considered time interval and that diagenesis has not obliterated the sediment provenance signature in such a relatively short time span. The only major diagenetic process is the formation of carbonate concretions (caliche), which can be easily recognized as secondary particles during point counting of thin sections.These results indicate that the reconstruction of the recent evolution of the local drainage system is possible simply by comparing ancient with modern fluvial sand compositions.On the other, the sand sediments older than the Neolithic, and approximately older than 10.000 years, show a significant shift in composition from the modern ones, with an overall increase of quartz and feldspar components. These compositional variations can be explained by the combination of various factors: a significant change in the bedrock lithology (neotectonic effect), climate changes related to glacial-interglacial phases which induced a variation in bedrock alteration, erosion and sand deposition rates (climate effect), and the post-depositional changes that may have varied the sand composition (diagenetic effect). Further studies, now in progress, will permit a better characterization of the sediment supply through space and time, possibly allowing the reconstruction of the sand composition in the older local drainage system as response and interplay among neotectonics, climate changes and diagenesis.
2003
- Anatomy of carbonate turbidite mega-beds (M. Cassio Formation, Upper Cretaceous, northern Apennines, Italy).
[Articolo su rivista]
Zuffa, G. G.; Fontana, Daniela; Morlotti, E.; PREMOLI SILVA, I.; Sighinolfi, G. P.; Stefani, C. FONTANI L.
abstract
Turbidites mega-beds are the product of convulsive sedimentary events and provide time lines for the study of the stratigraphic record. An integrated and detailed study of depositional facies, petrography. paleontology and geochemistry of Cassio mega-beds allows: 1) determination of individual sediment types stored before resedimentation: 2) recognition of source area locations, types of triggering mechanisms, and transport/depositional processes, bottom fauna ecologu and diagenetic modifications.
2003
- Carta Geologica Regionale alla scala 1:25.000 della Regione Emilia-Romagna, "Monghidoro"- 237 SE. Foglio 237 "Sasso Marconi".
[Cartografia]
Panini, Filippo; Bettelli, Giuseppe; Pizziolo, M. con contributi di AMOROSI A.; Basoli, R.; Bonazziu, ; Borsetti, A. M.; Capitani, M.; Fioroni, Chiara; Fregni, Paola; Fontana, Daniela; MANTOVANI UGUZZONI, Maria Pia
abstract
-
2003
- Carta Geologica Regionale alla scala 1:25.000 della Regione Emilia-Romagna, "Sasso Marconi- 237 NE. Foglio 237 "Sasso Marconi".
[Cartografia]
Panini, Filippo; Bettelli, Giuseppe; Pizziolo, M. con contributi di AMOROSI A.; Basoli, R.; Bonazzi, Ugo; Borsetti, A. M.; Capitani, M.; Fioroni, Chiara; Fregni, Paola; Fontana, Daniela; MANTOVANI UGUZZONI, Maria Pia
abstract
-
2003
- Carta Geologica Regionale alla scala 1:25.000 della Regione Emilia-Romagna, "Savigno- 237 NO. Foglio 237 "Sasso Marconi"
[Cartografia]
Panini, Filippo; Bettelli, Giuseppe; Pizziolo, M. con contributi di AMOROSI A.; Basoli, R.; Bonazzi, Ugo; Borsetti, A. M.; Capitani, M.; Fioroni, Chiara; Fregni, Paola; Fontana, Daniela; MANTOVANI UGUZZONI, Maria Pia
abstract
-
2003
- Carta Geologica Regionale alla scala 1:25.000 della Regione Emilia-Romagna, "Vergato"- 237 SO. Foglio 237 "Sasso Marconi". S.EL.CA Firenze
[Cartografia]
Panini, Filippo; Bettelli, Giuseppe; Pizziolo, M.; CON CONTRIBUTI, Di; Amorosi, A.; Basoli, R.; Bonazzi, Ugo; Borsetti, A. M.; Capitani, M.; Fioroni, Chiara; Fregni, Paola; Fontana, Daniela; MANTOVANI UGUZZONI, Maria Pia
abstract
-
2003
- Composition of fuvial sands as a tool to unravel recent sedimentation history of the Modena plain (Italy)
[Relazione in Atti di Convegno]
MARCHETTI DORI, Simona; Fontana, Daniela; Lugli, Stefano
abstract
Composition of fluvial sand can represent an important tool to reconstruct the sadiment evolution of the Po plain during the Quaternary.
2003
- Diapiric mud breccias: modern and ancient examples (northern Apennines, Italy).
[Relazione in Atti di Convegno]
Conti, Stefano; Fontana, Daniela; Gubertini, A.
abstract
Composition and architecture of polygenic breccias actually extruded from the Modena-Reggio mud volcanoes have allowed insight into the genesis of similar chaotic deposits associated to ancient cold seep chemoherms in the northern Apennines. Both cold seeps and mud volcanoes result from rising and expulsion of variable amounts of hydrocarbon-rich fluids at the sea floor or in continental areas, and are the locus of abundant brecciated sediments. Subaerial mud volcanoes have a pattern of activity similar to submarine mud volcanoes: they present short eruptive periods with emission of chaotic breccias floating in a viscous mud, thus producing debris flows. Polygenic breccias extruded from their cones and craters show sedimentological features similar to monogenic and polygenic brecciated lithofacies observed in fossil methane-derived carbonates. These affinities suggest that autobrecciated structures and exotic sediments in fossil chemoherms are probably related to the offscraping and chaotic mixtures of sediments during the rapid fluid rise along diapiric conduits or fractures, following the same processes and mechanisms as in chaotic deposits associated with shale diapirs and mud volcanoes. Our data suggest a relationship between extruded sediments and substratum typology: mud breccias with polygenic clasts are associated with a geological substratum including sedimentary mélanges and olistostromes. It is possible that the block-in-matrix textures of these poorly consolidated chaotic deposits favour the offscraping of exotic sediments and also the upward migration of fluids.Similarities between the examined fossil seep carbonates and mud volcanoes include also: - the type of fluids which consist mainly of methane mixed with connate waters and clay mud, and their isotopic signatures strongly depleted in δ13C values (fluid origin can be both thermogenic and biogenic); - the presence of a population of active sulphate reducing bacteria (by comparison with modern seep carbonates); - the occurrence of chaotic deposits; - the existence of thick, fine-grained, plastic sediments in the enclosing sedimentary succession; - the control of tectonic activity, particularly compressional activity.The comparison between recent and fossil diapiric-related structures has been useful for constraining the nature of the fossil seepage pathway, understanding fluid expulsion processes and reconstructing models of chemoherm evolution. In particular, this investigation suggests that brecciated structures and exotic sediments in ancient chemoherms are due to the offscraping and chaotic mixtures of sediments during the rapid rise of methanogenic fluids along diapiric conduits or fractures, following similar processes and mechanisms as in chaotic deposits associated with mud volcanoes.Finally, the strictly association of seep carbonates, autobrecciation related structures and chaotic deposits is a more useful criterium than structural foliations as proposed by various authors (Orange et al., 1990; Orange and Brown, 1993) in order to distinguish diapiric mélanges from other type of chaotic deposits, because original features of sedimentary bodies are usually modified by later sedimentary or tectonic processes.
2003
- Extrabasinal and intrabasinal sources in siliciclastic-carbonate turbidite systems of the northern Apennines.
[Articolo su rivista]
Fontana, Daniela
abstract
Ancient basin plain turbidite systems may be characterized by a complex sedimentary fill made up of an alternation of compositionally different types of beds which reflect multiple sources with complex relationships to the basin. Spectacular examples of mixed siliciclastic/carbonate turbidite systems are represented by the Upper Cretaceous Helminthoid Flysch in the northern Apennines.
2003
- Methane-related carbonates in the Miocene Apennine foredeep (Italy). Sedimentological, mineralogical and geochemical considerations.
[Relazione in Atti di Convegno]
Conti, Stefano; Fontana, Daniela; Gubertini, A; Sighinolfi, Gp; Tateo, F.
abstract
Seep carbonate deposits with very negative δ13C values (chemoherms) are documented from various tectonic settings such as convergent plate boundaries, active transform and passive continental margins. In the middle Miocene foredeep basin of the northern Apennines, several pelitic intervals intercalated within turbidite sediments include carbonate bodies interpreted as chemoherms on the basis of isotopic data (δ13C as low as – 41.33 ‰ PDB) and paleontological evidences. These bodies are associated to features of intense sediment instability such as slumps, intraformational breccias and olistostromes. Sedimentological, mineralogical, chemical and isotopic studies where carried out on in-situ carbonate bodies from two of these pelitic intervals in order to reconstruct fluid sources and chemoherm genetical mechanisms and to document the connection between fluid seepage and syndepositional tectonics. Massive (micritic) carbonate authigenic phases of chemoherms consist of low Mg- and Sr-calcite and/or aragonite. Non stoichiometric dolomite and minor amounts of sulphur phases (sulphides and Ca sulphate) are concentrated in the brecciated lower portion of the bodies. Main carbonate phases from the muddy sediments which host the chemoherms consist of high Mg- and Sr-calcite with minor amounts of non-stoichiometric dolomite. The turbidite sediments (Te interval) differ from the pelites by containing significant amounts of stoichiometric (detrital) dolomite. Mineralogical analysis of the carbonate phases reveals that chemoherm bodies are richer in detrital quartz and in chlorite- smectite and lower in illite than the surrounding pelites. Differences are also observed in the distribution of some paleoenviromental indicator elements (Ni, Co, Cu, Zn), which indicate unstable oxidative conditions during or after chemoherm precipitation. Isotopic data (δ13C values as low as –20.31 ‰ PDB) of carbonates from pelites that surround the chemoherms indicate that the carbon is at least in part of biogenic origin and probably related to diffusion of CO2 and methane-rich fluids through the sea floor around the main vents where chemoherms grow. Mineralogical (enrichment in smectite and dolomite, Ca sulphate precipitation) and chemical (high chlorine content) features of some chemoherm bodies suggest that the aqueous fluids associated to the seeping gas were highly saline brines of problematic origin. Some features suggest genetical analogies between the chemoherm deposition in the Miocene foredeep basin and present sedimentary conditions where gas hydrates are generated. It is hypothesized that the pelitic intervals represent sedimentary episodes on top of ephemeral structural highs related to blind faults linked to the advancement of Northern Apennine deformational front. It is possible that the growth of structural highs was an effective mechanism for concentrating gas hydrates by gradually raising the base of their stability zone. Gas hydrates or similar fluids could have played an important role in triggering sediment instability and slumping along the margins of structural highs. The relation between methane seepage, sediment slumping and tectonics suggests a reinterpretation of many chaotic deposits and soft-sediment deformation features as a product of the episodic release of overpressured shallow methane accumulations in slope sediments.
2003
- Modena si svela alla rete, un percorso culturale-virtuale nella città di Modena
[Articolo su rivista]
Bertacchini, Milena; Fontana, Daniela; Paltrinieri, N.
abstract
Percorso culturale virtuale che si snoda in un insolito paesaggio cittadino “Sottosopra” tra le acque e i canali sotterranei della città di Modena, tra luoghi apparentemente inusuali se pur inconsciamente vicini, con l’intento di fornire una visione globale e dinamica del territorio cittadino.
2003
- Sand production by chemical and mechanical weathering of well lithified siliciclastic turbidites.
[Articolo su rivista]
Fontana, Daniela; G. C., Parea; Bertacchini, Milena; P., Bessi
abstract
The production of sand by chemical and mechanical weathering in a temperate humid climate and in a middle altitude mountain area has been investigated by comparing the composition of the sandy fraction of ancient and recent soils with the composition of parent rocks and stream sands. We examined the drainage basins of two high-gradient streams in the northern Apennines (Ospitale and Fellicarolo) and a short portion of the Leo stream derived from their confluence. Bedrock is made of a single rock type, the siliciclastic arkosic turbidites of the Cervarola Formation, and only in the lower portion of the basin the Leo stream cuts carbonate and pelitic lithotypes of Ligurian units. River bed sands have a lithic composition and are very rich in sedimentary rock fragments such as shales, silstones and fine-grained arenites derived from the Cervarola tubidites beds. The variations observed in the quartz/lithics ratio is primarily explained with weathering conditions (in particular soil type and steepness of slope), and only subordinately seems to be related with the river transport. The change in outcropping rocks in the lower part of the basin is immediately reflected in the lithic fraction of stream sands, marked by micritic fragments indicating contribution from carbonate units.Soils sands show different compositions. Recent soils from the highest watershed areas have a lithic composition. The more developed older dark soils capping red soils, and the chemically more active black swampy soils, show compositions gradually richer in quartz and feldspars. Pedogenic reactions initially reduce the lithic fragments, leading to an indirect enrichment of the more resistant quartz and feldspar grains. It is likely that the quartz-feldspar rich composition of the black swampy soils is partially related to the coarser-grained arenites of the bedrock.Results from this study indicate that in a drainage basin cutting well lithified sedimentary rocks, rich in shale and siltstones, the chemical activity and duration of pedogenetic processes, and the steepness of valley slopes, which controls the intensity of physical breackage of outcropping rocks, are the major factors controlling the production and composition of sand sediments. In a temperate humid climate these two factors seem to work some what independently and give an imprint to the produced sediment which changes as a function of different topographic conditions. Physical breackage prevails on steep slopes, thus the sediments are rich in unstable lithic grains. Even in very acidic soils, alteration of feldspar seems to be not significant, probably because the time from the last glaciation has been not long enough to produce visible effects on feldspar grains.
2003
- Sediment instability triggered by gas hydrate dissociation: what can we learn from the fossil Northern Apennines ocean margin ?
[Relazione in Atti di Convegno]
Fontana, Daniela; Vannucchi, P.; Conti, Stefano
abstract
Gas migration and gas hydrates
2003
- The Modena-Reggio mud volcanoes (northern Italy): an actualistic model for the interpretation of Miocene authigenic carbonates related to fluid expulsion.
[Articolo su rivista]
Conti, Stefano; Fontana, Daniela; Gubertini, A.; Bussi, P.
abstract
The paper examined physical, geochemical and geological features, and fluid expulsion processes of fossil seep carbonates and recent mud volcanoes in the northern Apennines. Chaotic brecciated deposits associated with short “eruptive” periods of the Modena-Reggio mud volcanoes (Regnano) are debris flows made of polygenic breccias floating in a viscous mud. These deposits show a number of analogies with monogenic and polygenic brecciated lithofacies of the Miocene methane derived authigenic carbonates of the northern Apennines. Similarities between the examined fossil seep carbonates and mud volcanoes include also the type of fluids which consist mainly of methane mixed with connate waters and clay mud, and their isotopic signatures strongly depleted in δ13C values. The comparison between recent and fossil diapiric-related structures has been useful for constraining the nature of the fossil seepage pathway, understanding fluid expulsion processes and reconstructing models of chemoherm evolution. In particular, this investigation suggests that brecciated structures and exotic clasts in ancient chemoherms are due to the offscraping and chaotic mixing of sediments during the rapid rise of methanogenic fluids along diapiric conduits or fractures, following similar processes and mechanisms as in chaotic deposits associated with mud volcanoes.
2002
- A pelitic interval enclosing primary chemoherms in the M. Cervarola Formation (Northern Apennines): evidence for synsedimentary tectonics during the Miocene.
[Articolo su rivista]
Conti, Stefano; Fontana, Daniela
abstract
A decametric pelitic interval made up of marls and mudstones enclosing numerous carbonate bodies is present in the upper portion, Langhian in age, of the M. Cervarola Formation in the Bologna Apennines, between the Silla and Setta streams. A number of distinctive geometrical, sedimentological and compositional characteristics allow the carbonate bodies to be interpreted as authigenic carbonate buildups (primary chemoherms), related to methane venting. Chemoherms are always located in proximity of the tectonic contact separating the M. Cervarola Fm from the Sestola-Vidiciatico Unit. In this context, the expulsion of fluids was probably induced by tectonic compression and the chemoherms could be considered as syntectonic deposits related to structural highs. Syntectonics highs affected the early-middle Miocene sedimentation of foredeep turbidite units (M. Cervarola and Marnoso-arenacea formations) with pelitic turbidites overlapping structural reliefs, probably related with blind thrusts-fold drapes. Chemoherms within the pelitic intervals could be used as indicators of tectonic activity, as confirmed by the associated chaotic structures and slumps. These observations, and the comparison with the resedimented chemoherms occurring in other outrops of the M. Cervarola Fm. as well as in minor basins (Porretta-Suviana), are crucial to more accurate paleogeographic reconstructions of the middle Miocene foredeep.
2002
- Carta Geologica d’Italia a scala 1:50.000. Foglio N. 237 “Sasso Marconi”.
[Cartografia]
Panini, Filippo; Bettelli, Giuseppe; M. PIZZIOLO e. con contributi di A., Amorosi; R., Basoli; U., Bonazzi; Am, Borsetti; M., Capitani; Fioroni, Chiara; Fontana, Daniela; P., Fregni; M. P., MANTOVANI UGUZZONI
abstract
S.EL.CA., Firenze, Italy
2002
- Sediment instability related to fluid venting in Miocene authigenic carbonate deposits of the northern Apennines (Italy)
[Articolo su rivista]
Conti, Stefano; Fontana, Daniela
abstract
Chemosynthetic carbonates, identified by isotopic, paleoecological and sedimentological features, are concentrated in middle-late Miocene satellite and foredeep deposits of the northern Apennines. Chemoherms in the foredeep are hosted in thick pelitic intervals, probably deposited in intrabasinal structural highs, which are entirely or partly involved in large slumps, in many cases associated with extrabasinal slides. Sediment textures in carbonates and in the enclosing foredeep pelitic sediments indicate a link between hydrocarbon-fluid venting, sediment deformation and mobilization, and tectonics. The intensity and style of fluid release phases directly influenced chemoherm typology, and also determined overpressure conditions in low shear strength pelitic sediments, favouring sediment mobilization and influencing slope instability which widely affected the Apennine foredeep. Chemosynthetic carbonates are associated with sites of tectonically-fractured and compressed sediments in the Apennine foredeep-thrust belt system, thus indicanting a relation to the tectonic loading of the Apennine thrust-sheets which favoured fluid expulsion along forerunner faults. Possible gas hydrate contributions to fluid expulsion processes are discussed, based on sediment textures compared to modern vent areas. Finally, sediment instability may have facilitated large amount of fluid escape, thus stopping carbonate precipitation.
2002
- Strutture brecciate da emanazione di fluidi freddi: esempi attuali (Salsa di Regnano, RE) e fossili (chemioerme dell'Appennino Settentrionale di età miocenica).
[Relazione in Atti di Convegno]
Bussi, P.; Conti, Stefano; Fontana, Daniela; Gubertini, A.
abstract
I livelli di brecce associati all’attuale attività di un piccolo vulcano di fango nell’Appennino reggiano (Salsa di Regnano) presentano notevoli analogie con litofacies brecciate in carbonati autigeni fossili, di età miocenica medio-superiore, interpretati come il prodotto di associazioni biologiche chemiosintetiche (chemioerme) per risalita di fluidi freddi metanogenici sul fondo marino (cold seeps). La Salsa di Regnano, ritenuta uno dei più interessanti vulcanetti di fango dell’Appennino reggiano-modenese, è attualmente caratterizzata da emissione di fango molto liquido associato a bolle di idrocarburi gassosi, prevalentemente metano, e a tracce di petrolio ed acqua salata. La sua attività eiettiva ha portato alla costruzione di un cono principale di pochi metri d’altezza, con numerose bocche secondarie poste nell’area della salsa, e alla formazione di una colata che si estende verso la valle del Tresinaro, lunga circa un chilometro. La Salsa di Regnano è localizzata all’intersezione tra una importante faglia ad andamento antiappenninico (SO-NE) e faglie minori. In occasione di più intensa attività della salsa, generalmente in corrispondenza di attività sismica, assieme al fango marnoso-argilloso e ai normali prodotti di emissione, avviene la risalita di numerosi frammenti di roccia strappati ai sottostanti sedimenti attraversati. I clasti, generalmente spigolosi, hanno dimensioni variabili da pochi millimetri a diversi centimetri. Sono costituiti da varie litologie, tra cui le più frequenti sono arenarie, calcilutiti grigio-verdi, marne rosate e rocce ofiolitiche. La provenienza dei clasti è da successioni dei complessi Liguri e da depositi Epiliguri (Formazione di Ranzano e Montepiano). I clasti sono legati da una matrice marnoso-argillosa grigio-nocciola e costituiscono livelli di brecce poligeniche, intercalati alla pelite, di spessore fino a decimetrico ed estesi per numerosi metri a partire dalla bocca di emissione. La Salsa di Regnano costituisce una manifestazione “fredda” generata dalla risalita lungo fratture di fango trasportato da idrocarburi gassosi ed acqua vadosa in pressione, che in alcuni casi è in grado di strappare e trasportare clasti di dimensioni considerevoli: nel passato infatti sono stati segnalati anche blocchi di notevoli dimensioni (da decimetriche a metriche) trascinati dalle colate fino ad alcune decine o centinaia di metri di distanza dalla bocca di emissione.
2001
- Authigenic carbonates related to chemosynthetic activity in the Miocene foredeep deposits of the northern Apennines.
[Relazione in Atti di Convegno]
Conti, Stefano; Fontana, Daniela
abstract
Methane-derived chemosynthetic carbonates, identified by the peculiar isotopic signature and by paleoecological and sedimentological characters, are present in the middle-late Miocene foredeep deposits of the northern Apennines. They consist of authigenic carbonates and carbonate- cemented detrital sediments associated with chemosymbiotic taxa, and represent an excellent geological record of ancient hydrocarbon seepage processes on the sea floor related to the flourishmment of chemosynthetic communities. Chemoherms in the foredeep are hosted in thick pelitic intervals, deposited in structural highs, which are entirely or partly involved in large-sized slumps. Brecciated textures, as well as structures related to sediment instability processes, are commonly observed in carbonates. Brecciated limestones mark the sites where methane is episodically released explosively, frequently with the offscraping of exotic sediments during the rapid fluid rise along diapiric conduits or fractures. Widespread discharge of pore fluids lowers the shear strength of the sediments and triggers the movement of slumps or debris flows, which are frequently associated with chemoherms. Multiple phases of explosive breakage of micritic carbonates, diapirism, slumping, reworking processes as debris flows or local turbiditic events explain the chaoticization of many deposits associated with Miocene chemoherms of the northern Apennines. We suggest that the growing of structural highs was an effective mechanism for concentrating gas hydrates by gradually moving upward the base of their stability zone with subsequent decomposition, thus contributing to undermine the stability of slopes and inducing sediment deformation and failures.
2001
- STRATIGRAPHIC ARCHITECTURE AND COMPOSITION OF THE PERMIAN AND TRIASSIC SILICICLASTIC SUCCESSION OF NURRA(NORTHWESTERN SARDINIA)
[Articolo su rivista]
Fontana, Daniela; C., Neri; A., Ronchi; C., Stefani
abstract
This work representsa preliminary revision of the terrigenousPermian and Triassic stratigraphic successionso f theNurra region (northwestern Sardinia). On the basis of lithostratigraphical, sedimentological and petrographice evidence supported by scattered and rare biostratigraphical data, the wholepost-Variscan successiohna is subdivided into the followingunits: I) the "Punta Lu Caparoni Formation" (PLC), made by thetraditional lluvial-to-lacustrin depositsa II) a volcanic-bearing unit of problematic geochemistry, scarcely cropping out in the Lu Caparoni-Cala Viola area and well-documented in the Monte Santa Giusta section, where shows an alkaline composition; III) a clastic unit of reddish conglomerates sandstones and minor pelites, rich in volcanic-derived clasts.
2001
- The Miocene chemosynthetic communities of the Northern Apennines and the mechanisms of fluid release from a convergent margin.
[Relazione in Atti di Convegno]
Conti, Stefano; Fontana, Daniela; Vannucchi, P.; Bettelli, Giuseppe; Panini, Filippo
abstract
The Miocene cold seep communities of the northern Apennines
2000
- Cold vent processes in the Miocene Foredeep – thrust belt system of the Northern Apennines
[Relazione in Atti di Convegno]
Conti, Stefano; Fontana, Daniela; Vannucchi, P; Bettelli, Giuseppe; Panini, Filippo
abstract
Micritic limestones locally called "calcari a Lucina" packed with dense large bivalves and characterized by autoclastic breccias and fluid-flow conduits are present in middle-late Miocene sediments of the northern Apennines. After many years of geologic controversies, these limestones have been reinterpreted as cold vent deposits, thus becoming special indicators of clathrate dissociation and revealing important relationships between methane seepages, sediment instability, and tectonics.Chemoherms are found from internal tectonic zones (satellite Epiligurian basins) to external ones (foredeep turbidites) of the Apenninic chain. Dominant rock types are calcilutitic limestones, marly limestones and calcarenites; they are composed of authigenic micrite associated with minor neoformed pyrite, biogenic particles and siliciclastic detritus. Host sediments are mudstones, muddy sandstones and marlstones; characterised by low permeability but commonly fractured. In the foredeep chemoherms occur within thick pelitic intervals, deposited in structural highs, which are entirely or partly involved in slumps, frequently associated with extraformational slides. In this contest, chemoherms seem to be indicators of the advancing deformational front of the chain, thus heralding main tectonic phases. Otherwise, in the satellite basins, the distribution of chemoherms is not structurally controlled; a relationship between periods of sea level drops and clathrate destabilization processes in these relatively shallow successions should be taken into account.Two main types of chemoherms, respectively related to focussed and diffuse methane-rich flux venting, can be distinguished in the field. The first type consists of huge isolated lenticular carbonate to calcarenitic levels ranging in extension from 15 to 200 m and a maximum thickness up to 30 m. The second type of chemoherm consists of numerous horizontally and vertically scattered marly-calcareous and calcarenitic lenses with a diameter from decimetric to 5-7 m and a thickness from some dm to 3-5 m. Chemoherm autobrecciation marks the sites where ponded methane at shallow depth is episodically released explosively, as also testified by the offscraping of exotic sediments during the rapid fluid rise along diapiric conduits or fractures. As a whole, widespread discharge of pore fluids lowers sediment shear strength and permits the movement of slumps or debris flows, which are frequently associated with chemoherms.
2000
- Primary chemoherms in the Mt. Cervarola Formation (Bologna Apennines): a tool in understanding the evolution of the Northern Apennines during the Miocene.
[Relazione in Atti di Convegno]
Conti, Stefano; Fontana, Daniela; Righetti, L.
abstract
In the upper portion of the Mt. Cervarola Formation in the Bologna Apennines, between the Silla and Setta streams, a decametric level made up of marls and mudstones intertongued with numerous carbonate bodies crops out. Based on preliminary biostratigraphic data, the age of these deposits is Langhian. A number of distinctive geometrical, sedimentological and compositional characteristcs allow the carbonate bodies to be interpreted as primary chemoherms, related to methane venting. They consist of micritic, marly calcareous to calcarenitic lenses, strongly brecciated and very rich in densely packed lucinid bivalves. The dimensions vary from a few decimeters to several meters and the thickness ranges from 20-30 cm to 4-5 m. Carbonate lenses are horizontally and vertically scattered and grade into the surrounding pelitic sediments with transitional lithologies in between. The methanogenic carbonates consist of authigenic micrite associated with neoformed pyrite; the micritic groundmass is commonly accompanied by abundant bioclastic debris and scarse fine-grained detritus. Brecciated structures are common, represented by monomictic and polymictic breccias, dense networks of non systematic carbonate-filled veins and fractures, and extensive vuggy fabrics. Other features, such as micritic doughnuts, nodular and cylindrical to encircling concretions and pipe-like structures, are interpreted as fluid-flow conduits. Chaotic structures are rare, consisting of small slumps involving marly and carbonate deposits.The recognition of primary chemoherms in the Mt. Cervarola Formation indicates that synsedimentary mobilization (cannibalism) was frequent not only in slope pelites but also in foredeep deposits. In fact, lucinid-bearing deposits occur in the Mt. Cervarola turbidites in various areas, such as Bobbio and Segavecchia, and in minor basin successions (Porretta, Suviana). They are not chemosynthetic and are reworked, consisting of lucinid clasts occurring at the base of resedimented arenite beds. A minor reworking is evident in the problematic Barigazzo outcrop, made up of limestone blocks with biogenic debris and disarticulated bivalve shells. Lucinid clasts and blocks come from different sources, such as the Mt. Cervarola primary chemoherms, intraformational argillaceous levels including chemoherms but no more preserved, and adjacent slope pelites (Vicchio Marls). The primary chemoherms in the Mt. Cervarola Fm from the Bologna Apennines are remarkably similar to the time-equivalent (Langhian) deposits of the inner Marnoso-arenacea Fm cropping out on the right side of the Sillaro line. In both cases chemosynthetic carbonates are enclosed in argillaceous lithofacies, probably draping over folds and thrust top. They may indicate interruption of normal turbidite deposition and could be used as indicators of tectonic activity, as confirmed by the associated chaotic structures and slumps. These observations are crucial to more accurate paleogeographic reconstructions of foredeep and minor basins (Porretta-Suviana) during the middle Miocene.Finally, the relationships among methane-derived authigenic carbonates, venting of methane rich fluids and tectonic activity are testified by the peculiar position of the Mt. Cervarola primary chemoherms. They are located in proximity of the tectonic contact separating the Mt. Cervarola Fm from the Sestola-Vidiciatico Unit, and are aligned along the overturned limb of an anticline. In this context, the expulsion of fluids was probably induced by tectonic compression and the chemoherms could be considered as syntectonic deposits. This has broad implications for constraining the age and the evolution of the structural setting.
1999
- Brecciated structures and fluid-flow conduits as indicators of methane-derived carbonates (northern Apennines, Italy).
[Articolo su rivista]
Conti, Stefano; Fontana, Daniela
abstract
The recognition of fossil carbonates as products of microbial chemosynthesis associated with fluid and hydrocarbon venting at the sea floor (chemoherms) has been linked to two main indicators (Sakai et al., 1992; Terzi et al., 1994; Kelly et al., 1995; Corselli and Basso 1996): the marked depletion in carbon isotope composition of the authigenic carbonates and the low diversity/high abundance of benthic chemosymbiotic communities (densely packed mussels and clam bivalves, gastropods, tube worms). Nevertheless, not all methane-derived carbonates enclose remains of large chemosymbiotic taxa, making the recognition of unfossiliferous methanogenetic limestones in the field problematic. Recently, new studies (Cavagna et al., 1998; Conti and Fontana, 1998) have shown that other diagnostic criteria, such as geometric, sedimentologic and compositional characteristics, can be useful in the identification of fossil seep environments and associated carbonates. In particular, brecciated structures and fluid-flow conduits, which frequently occur in methane-related carbonates, are of outstanding importance in connecting fluid ventings, slumping of pelitic sediments and tectonics. Indeed, these structures could permit the reinterpretation of many chaotic deposits as due to diapiric processes.Carbonate deposits bearing fossil chemosynthetic assemblages are concentrated in middle-late Miocene of the northern Apennines and are found in various domains and basin types (Vai and Ricci Lucchi, 1994; Conti and Fontana, 1998): from internal tectonic zones (Epiligurian basins) to external ones (foredeep). Enclosing sediments are mudstones, muddy sandstones and marlstones; commonly they have low permeability but are severely fractured. They are present in syntectonic deposits, related to compression and thrusting of the Apennine chain. In the foredeep, chemoherms are moderately reworked and concentrated in slumped pelitic horizons, suggesting a close relationship between sediment instability and hydrocarbon-fluid venting. Field and petrographic examination of methane-derived carbonates permits different lithofacies to be recognized: light blue to dark grey micritic limestones, biomicritic marly limestones, light brown to grey calcareous marls, fine to coarse calcarenites, calcarenitic limestones and various types of calcareous breccias and fractured limestones.
1999
- I Beni Geologici della Provincia di Modena
[Monografia/Trattato scientifico]
Bertacchini, Milena; Bettelli, Giuseppe; Bonazzi, U.; Capedri, S.; Capitani, M.; Castaldini, Doriano; Conti, Stefano; Corradini, D.; Fioroni, Chiara; Fontana, Daniela; Fregni, P.; Gasperi, G.; Giusti, C.; Lugli, Stefano; Marchetti, Mauro; Panini, Filippo; Panizza, M.; Pellegrini, M.; Piacente, S.; Rossi, A.; Soldati, Mauro; Tosatti, G.
abstract
Sono presentati, sotto forma di schede, i beni geologici (o geositi) censiti nella Provincia di Modena. Le schede sono state aggregate in cinque paragrafi: Beni geomorfologici, Fluidi sotterranei, Esposizioni di valore stratigrafico e strutture sedimentarie, Esposizioni di strutture tettoniche, Ofioliti. Si è cercato di privilegiare da un lato una guida scientifica alla geologia della Provincia e dall'altro di segnalare un alto numero di siti allo scopo di salvaguardare il più possibile l'ambiente modenese, caratterizzato, in molte sue parti, da un'intensa e continua antropizzazione.
1999
- Miocene chemoherms of the northern Apennines, Italy
[Articolo su rivista]
Conti, Stefano; Fontana, Daniela
abstract
In the Miocene of the northern Apennines, methane-derived limestones from various geologic settings represent important examples of fossil chemoherms and provide a basis for more accurate interpretations of seepage systems. The systematic study of fossil chemoherms has allowed the definition of new field and compositional criteria for the recognition of these deposits, which were previously based almost exclusively on negative carbon isotope composition and peculiar chemosynthetic communities; this has constrained the relations between seepage and sedimentary and tectonic instability processes. We suggest that the peculiar brecciated structures associated with fossil chemoherms are related to diapirism or overpressured pelitic sediments due to fluid venting. Fluidization of sediments increases the instability of mudstones in which chemoherms are contained, thus favoring gravity slumping processes and the reworking of many chemoherms.
1998
- Caratteri stratigrafici e composizionali della Formazione delle Argille Varicolori (Cretaceo superiore, Appennino modenese e reggiano)
[Articolo su rivista]
Bertacchini, Milena; Bettelli, Giuseppe; Fontana, Daniela
abstract
vengono illustrati i caratteri stratigrafici e sedimentologici delle argille varicolori (complessi Liguri) nell'Appennino settentrionale, con particolare riferimento alla natura composizionale e alla genesi dei livelli verdi e rossastri che si alternano nella successione
1998
- Geochemical history of calcite precipitation in Tertiary sandstones, northern Apennines, Italy. In "Carbonate cementation in sandstones " (S.Morad Ed.)
[Capitolo/Saggio]
Mcbride, E. F.; Milliken, K. L.; Cavazza, W.; Cibin, U.; Fontana, Daniela
abstract
In order to better understand the origin and controls of calcite cementation in marine sandstones, we studied ten tertiary lithostratigraphic units exposed in the northern apennines, Italy, which display a variety of pattern of calcite cement
1998
- Recognition of primary and secondary Miocene lucinid deposits in the Apennine chain.
[Articolo su rivista]
Conti, Stefano; Fontana, Daniela
abstract
The examination of about eighty exposures of lucinid deposits of the Apennine chain based on new field analyses and previous data, and the compositional study of one hundred samples representative of the different geological settings in which lucinid assemblages are found, enable us to distinguish four types of deposits. Type 1 and type 2 are primary (autochthonous) deposits whereas type 3 and type 4 are secondary (allochthonous) deposits. Type 1 deposits consist of marly-calcareous and calcarenitic lenses or columnar bodies, jammed with articulated lucinid-like shells, usually belonging to oligotypic communities and grading into the surrounding pelitic sediments. Most of the samples are made of homogeneous micrites, biomiocrites and fossiliferous micrites, containing variable amounts of biogenic particles, chiefly planktonic foraminifera. Type 2 deposits are made up of lucinid shells, either isolated or associated with a more diverse fauna, in mudstones, marls, arenitic and calcareous marls. Type 3 deposits are constituted of carbonate olistoliths enclosed as blocks within chaotic horizons in turbiditic and hemipelagic formations of the Miocene foredeep. Type 4 deposits are represented by coquina debris, isolated articulated or disarticulated shells in resedimented arenites, calcarenites, carbonate breccias with biogenic debris. Samples of secondary deposits show a noticeable variety of lithologies and textures and are very heterogeneous even at the microscopic scale. The most common lithotypes include fine to medium grained arenites characterized by a loosely detrital fabric and by a pervasive micrite cement. Fossiliferous micrites and biomicrites with brecciated textures are common. The detrital framework show striking similarities to the composition of the host turbidites. Carbonate intraclasts and clasts deriving from lithotypes of the ligurian domain are present. Most of the type 1 and 3 deposits are strongly 13C depleted and are interpreted as chemosynthetic communities (chemoherms), with authigenic carbonate deposition related to methane-rich fluid venting. Type 1 deposits occur only in thick pelitic sediments belonging to the satellite (Termina Formation of the epiligurian sequence) and to the foredeep basins (Vicchio and Letto Marls). Type 2 deposits are instead related to normal marine conditions, whereas the type 4 could have their source from all the other types of deposits. Secondary lucinid deposits occur in a wide range of different tectonic setting, from backland to foreland, with a concentration in the middle Miocene foredeep. The secondary lucinid deposits of the foredeep turbidites evidenced several different grades of allochthony and multiple provenances. Lucinid deposits in the Marnoso-arenacea turbidites show evidence of a moderate reworking, probably from the enclosed pelitic horizons or from adjacent slope pelites. The source of the oldest chemoherms seems to be represented by the Vicchio Marls, whereas isolated shells and coquina debris in resedimented beds of the minor basins and Cervarola foredeep probably originate from satellite basins or from methane-derived biological communities located in fine-grained horizons no longer preserved. The peculiar brecciated structures observed in many lucinid chemoherms are probably the result of a number of superimposed processes, involving fluidization of sediments and reworking for gravity mass transport. Mud diapirism and/or injection, related to overpressuring of sediments due to methanogenic fluid venting, could account for the formation of the brecciated structures resembling those related to gravity flow processes. Fluidization of sediments may also represent an important mechanism able to increase the instability of pelitic marly sediments, thus favouring gravity slumping processes.
1998
- Sedimentation pattern and composition of Tertiary Ligurian Flysch of the northern Apennines: the Monte Sporno and Marne rosate di Tizzano formations
[Articolo su rivista]
Fontana, Daniela; G., Faggiano; M., Marastoni
abstract
The paper presenis a detailed stratigraphical analysis coupled with the compositional study of two mixed carbonate-siliciclastictu rbidite successionso f Paleocene-Eocenea se in the northern Apennines: the Monte Soornoand Marne rosate di Tizzano formations. The bed by bed measure of more than 1000m of the M. Sporno succession and of significant portions of the basal (Bersatico) and upper (Castelmozzano) members of the Màrne rosate Fm has allowed the recognition of the different types of turbidite beds and hemipelagites which alternate in the successionsand an estimate of their frequency and cumulative thickness. Turbidites vary from thin-bedded arenitic siliciclasticbeds to carbonate and mixed megabeds, and show a remarkable internal variability. The M. Sporno Fm consists of a monotonous successiono iturbidites and hemipelagites,without evident verrical trend except for a slight increase of pelitic lithologies up section. Otherwise, the lower and upper members of the Marne rosate Fm are characterized by a distinct stratigraphic framework. The lower Bersatico Member is dominated by carbonate and mixedbeds and megabedsa nd showsa broad similarity with the M. Sporno succession The upper Castelmozzano memberis made chiefly of thin-bedded arenitic siliciclastic beds, and carbonate beds are subordinate. The sediment is suppliedto the basin by a number of sources, primarily inmabasinal pelagic and shelfal areas which produced the abundantbiogenic carbonate detritus
1997
- Lucinid deposits from different geological settings of the northern Apennines.
[Relazione in Atti di Convegno]
Conti, Stefano; Fontana, Daniela
abstract
Sixty exposures of lucinid deposits ("calcari a Lucina" of the literature) in different depositional and tectonic settings of the northern Apeninnes, from backland (satellite and minor basins) to foredeep (turbidites and closure deposits) and foreland (Sicily), were studied and, in many cases, reinterpreted in the field. Field and compositional data show that lucinid deposits include not only peculiar carbonate blocks, but a variety of lithologies and fossil assemblages: micritic limestones, marly limestones, mudstones, marls and arenitic marls, fine to coarse-grained arenites, fine to coarse-grained calcarenites, carbonate monomictic and polymictic breccias and microconglomerates. The fossil content is not only adscribable to the genus Lucina, but more generally to lucinids or other bivalves. Lithological and compositional characters are mainly controlled by the depositional and tectonic setting. Lucinid deposits from satellite basins and foredeep slope sediments show evidences of primary deposition while those included in foredeep turbidite deposits are clearly reworked. In some cases only isolated shells are reworked. Primary lucinid deposits occur as: - type 1) marly-calcareous and calcarenitic lenses or column-like bodies, crowded with articulated specimens usually representing the dominant fauna of an oligotypic community; these lenses are often clustered but not related to a precise stratigraphic level and they gradually pass to the host sediments (marly mudstones); - type 2) isolated specimens or associated with a dense high diversity fauna in mudstones, marls, arenitic and calcareous marls. Secondary lucinid deposits occur as: - type 3) carbonate olistoliths crowded with articulated or disarticulated specimens associated with an oligotypic fauna; they are usually enclosed within chaotic horizons made up of intraformational slumps, ligurian-subligurian olistostromes, ligurian-epiligurian olistoliths, resedimented arenitic beds and polymictic breccias, intercalated in turbiditic formations; - type 4) coquina debris, isolated articulated or disarticulated shells, (in few cases associated with abundant fauna from shelf areas) in resedimented arenites, calcarenites, carbonate breccias with biogenic debris (debrites). Most of the type-1 and type-3 deposits are strongly 13C depleted, and are interpreted as chemosynthetic communities (pseudobioherms) with authigenic carbonate deposition related to methane-rich fluid vents.Petrographic data show that the composition of the siliciclastic fraction present in lucinid deposits is consistent with the composition of the host deposits. Lucinid deposits included in the foredeep turbidites of the Marnoso-arenacea and Cervarola Formations display a wide variety of textures and lithologies. Most of the samples are characterized by a sort of "chaotic" texture with an abundant terrigenous fraction associated with micritic intraclasts and planctonic foraminifera. The interstitial fraction is made of micrite, but microspatic to spatitic calcite cements and patchy poikilotopic calcite are also present. The composition of the terrigenous fraction shows a great similarity with the composition of the including turbidites, thus indicating only an intrabasinal reworking of lucinid deposits. In primary, non reworked lucinid deposits of the epiligurian (Termina Formation) and slope sediments (Vicchio and Letto Marls) the terrigenous fraction is absent or very scarse and fine-grained. Samples show more homogeneous textures and lithologies, mainly represented by micritic to biomicritic limestones; planctonic foraminifera are abundant. Detrital carbonate clasts of ligurian affinity are sometimes present in epiligurian lucinid outcrops.According to this study, primary pseudobioherms occur only in epiligurian and foredeep closure pelitic sediments, rich in organic matter. Lucinid deposits in the Marnoso-arenacea and Cervarola foredeep turbidites show evidence of a moderate reworking probably from adjacen
1996
- La successione Monte Venere - Monghidoro nell'Appennino modenese e bolognese
[Articolo su rivista]
Fioroni, Chiara; Fontana, Daniela; Panini, Filippo; Parmeggiani, F.
abstract
-
1995
- HETEROGENEOUS DISTRIBUTION OF CALCITE CEMENT AT THE OUTCROP SCALE IN TERTIARY SANDSTONES, NORTHERN APENNINES, ITALY
[Articolo su rivista]
E. F., MC BRIDE; K. L., Milliken; W., Cavazza; U., Cibin; Fontana, Daniela; M. D., Picard; G. G., Zuffa
abstract
Calcite cement derived intraformationally in seven stratigraphic units of marine origin (five submarine-fan deposits and two shelf deposits) is distributed heterogeneously at the outcrop scale. Sandstone beds intercalated with calcareous shale older than Pliocene tend to be completely cemented, whereas stacked sandstone beds that lack shale interbeds have calcite cement in the form of tightly cemented concretions that make up only 10-30% of a bed. The abundance and distribution of concretions, with few exceptions, are irregular and unpredictable. Concretion shapes include spheres (<1 m diameter), oblate and prolate spheroids (<1.5 m), tabular forms (to 8 m long), and irregular forms. Patterns of concretions within beds are remarkably varied and include both random and uniform spacing; preference for either the top, middle, or bottom of beds; preference for faults that cut bedding at a high angle; and localization around shale rip-up clasts. There is no preference of concretions for shell-rich layers. Some formations have cement patterns specific to that formation, whereas other formations have different patterns at different outcrops. Most formations have more than one cement pattern in an outcrop. The lack of strong textural (grain size, graded bedding) or compositional controls on the localization of calcite cement suggests the preeminence of highly localized hydrologic factors in determining the spatial distribution of authigenic pore-filling calcite. Spherical concretions grew by diffusive supply of intraformationally derived components, whereas prolate and elongate concretions grew chiefly under the influence of advective supply. Faults apparently served as fluid conduits and were selectively cemented. In general, only sandstones intercalated with shale are totally cemented. This indicates that shales were a major source of cement components for these sandstones at least.
1994
- Sedimentology, palynostratigraphy and sequence stratigraphy of a continental to shallow marine rift-related succession: Upper Permian of the eastern Southern Alps (Italy)
[Articolo su rivista]
F., Massari; C., Neri; P., Pittau; Fontana, Daniela; C., Stefani
abstract
The Upper Permian deposits (Val Gardena Sandstones) of the eastern Southern Alps display the typical features of early rift succession onset of sedimentation after a long period of subaerial erosion, and upward fining trend from red beds through evaporites to marine carbonates.
1994
- THE UPPER CRETACEOUS HELMINTHOID FLYSCH OF THENORTHERN APENNINES: PROVENANCE AND SEDIMENTATION
[Articolo su rivista]
Fontana, Daniela; E., Spadafora; C., Stefani; S., Stocchi; F., Tateo; G., Villa; G. G., Zuffa
abstract
The Mt. Cassio, Mt. Caio, Mt. Antola and Solignano successions (Campanian to Maastrichtian) examined in the type localities are made up of three distinct types of turbidite beds: micritic-marly, arenidc-siliciclastic and mixed. The mixed beds exhibit an arenitic-siliciclastic interval sradins upward into a micritic-marly interval.The micritic-marly beds and the micritic-marly intervalsof mixed beds consist chiefly of penecontemporaneous coccolithsplus a clay component indicating resedimentarion ofcoeval pelagic mud and ponions of the underlyingsedimentary successions from structural isolated highs andmarginal shelves. The terrigenous detritus of silióiclasúcbeds and of basal intervals of mixed beds derives mainly fromgranitic and lo\4'- to medium-grade metamorphic rocks of acontinental basement and, in the case of Mt. Caio and Mt.Cassio, from a carbonate sedimentary cover.In the Mt. Cassio siliciclastic beds and intervals of mixedbeds, unlithifred squeezed grains of mudstones with Calpionellidaeand Calcisphamrlidae and argillaceous clasts arepresent, suggesting resedimentation of material from older,still unconsolidated successions. The si-liciclastic beds and intervalsof the Mt. Cassio succession also contain significantamounts of allochems characteristic of the photic àne. indicatingcontributions from Campanian to Màasuichrian-carbonate-pladorm systems
1994
- The Miocene Bismantova Fm. in the Vetto-Carpinetisyncline (Parma;Reggio Emilia Apennines):evolution of sediment provenance
[Articolo su rivista]
Fontana, Daniela; E., Spadafora
abstract
The main framework components and the type of lithic fragments of the Bismantova succession, define three petrofacies which can be matched with distinct lithostratigraphic units: the shelf basal members (Pietra di Bismantova, M.Castelletto, Pantano and Cigarello), the Vetto and the Maroia turbidites.Shelf arenites from the basal members are hybrid arenites. They are characterized by abundant intrabasinal carbonate grains, such as shallow-water bioclasts of Miocene age, indicating a consistent intrabasinal supply during deposition. The terrigenous componentcontains serpentinite and serpentine-schist rock fragments. The latter have long been considered as diagnostic of an alpine source. In this study we suggest that these clasts were derived mainly from the underlying Epi-Ligurian Fms., which are very rich both in metamorphic and ophiolitic debris of alpine and apenninic affinity. This petrofacies, characterizingthe Bismantova lower members, spans from the Reggio Emilia to the Bologna Apennines. The deposition of the Vetto and Marola turbidites marks a change in source-rocks. In the Vetto areìites, a large population of lithic fragments such as micriiic limestones, siltstones, shales, indicates detrital contributions mainly from the sedimentary successions of the Ligurian units.The terrigenous material of the Marola arenites derived from various sedimentary units:carbonate Ligurian units, the shelfal calcarenitic and arenitic lithotlpes of the basal Bismantova succession, but mainly arkosic sandstones (Loiano or Monghidoro?) able to release abundant quartz and feldspar grains.
1993
- COMPARISON OF COMPOSITION AND TEXTURE OF CALCITE-CEMENTED CONCRETIONS AND HOST SANDSTONES, NORTHERN APENNINES, ITALY
[Articolo su rivista]
Cibin, U; Cavazza, W; Fontana, Daniela; Milliken, Kl; Mcbride, Ef
abstract
Compositional and textural characteristics of 13 calcite-cemented concretions are compared with those in adjacent but essentially uncemented host sandstones to test the belief that concretions better preserve original detrital compositions than do host rocks. Sandstones sampled are from five upper Eocene to Pliocene clastic units deposited in a piggy-back setting and from one Miocene unit in the foreland basin of the northern Apennines. The intergranular volume of the sandstones indicates that in younger piggy-back units calcite cement was introduced after maximum burial or nearly so, whereas in older and more deeply buried piggy-back and foreland units minor compaction continued in host sandstones after concretion growth stopped. The concretions differ little from their host sandstones in bulk framework composition, abundance of detrital carbonate grains, and chemistry of feld-spars. Detrital grains in concretions, however, underwent a six-fold greater degree of calcite replacement than detrital grains in host samples. Four of six formations have no difference in relative abundance of heavy minerals between concretions and host sandstones. The two units showing significant differences in the heavy-mineral content are those that underwent deeper burial and higher temperatures, as shown by independent evidence. In the Ranzano Formation epidote is up to three times more abundant in concretions than in host samples, and other unstable species are present only in the concretions. In the Marnoso Arenacea Formation hornblende is twice as abundant in the concretions than in host sandstones. In these two units pore-occluding calcite cement in concretions probably prevented contact with corrosive formation water, whereas the host sandstones lost significant fractions of these unstable species. Thus, our data indicate that calcite-cemented concretions do not necessarily preserve unstable grains more readily than host sandstones, especially if cementation occurs late in the burial history of the sandstones. In the examined formations the main factors controlling the capability of concretions to preserve unstable framework grains seem to be (1) the types of unstable grains, (2) their susceptibility to dissolution by interstitial fluids or replacement by calcite, (3) burial depth and temperature during and after concretion development, and (4) time. Correct provenance reconstructions of sandstone units containing concretions must be preceded by assessment of any diagenetic alteration affecting the framework grains of both concretions and host rocks.
1991
- DETRITAL CARBONATE GRAINS AS PROVENANCE INDICATORS IN THE UPPER CRETACEOUS PIETRAFORTE FORMATION (NORTHERN APENNINES)
[Articolo su rivista]
Fontana, Daniela
abstract
The Upper Cretaceous Pietraforte Formation, an allochthonous unit of the Ligurian domain in the northern Apennines, provides a case study of the importance of detrital carbonate grains for provenance determination in sandstones. The Pietraforte Formation is composed of turbidite sandstones with subordinate conglomerate, deposited in an external sector of the Ligurian ocean, close to the Adriatic margin. The sandstones have a lithic composition, characterized by abundant sedimentary and metasedimentary rock fragments (35-56% of the terrigenous framework), little feldspar (< 7%) that is almost exclusively plagioclase, and a high ratio of fine-to coarse-grained polycrystalline quartzose grains to total quartzose grains (average Q(p)/Q(t) = 0.37). Carbonate rock fragments dominate the lithic association of both sandstones and conglomerates and provide the most detailed information for provenance determination. They are composed primarily of dolostones and a wide variety of limestones containing identifiable age-diagnostic microfossils. Fossils and rock textures of carbonate clasts document the erosion of Upper Triassic to Lower Cretaceous shelf and pelagic carbonate units which can be matched with Mesozoic rock types present in the Tuscan domain of the northern Apennines. Compositional results constrain the source of the Pietraforte Formation sandstones to the western margin of the Adriatic plate, from uplifted sedimentary and metasedimentary rocks of the Tuscan domain and its low-grade metamorphic basement. Coeval intrabasinal sources provided additional supplies to the depositional basin of the Pietraforte Formation; this intrabasinal supply consists of shelf carbonate allochems, planktonic foraminifera and argillaceous rip-up clasts. The presence of carbonate grains from shallow-water environments may indicate the existence during deposition of marginal shelf areas favourable for carbonate allochem production.
1990
- Il Flysch di Solignano nel quadro dei Flysch a Helmintoid (Maastrichtiano inferiore, Appennino settentrionale)
[Articolo su rivista]
Fontana, Daniela; C., Stefani; G. G., Zuffa; F., Tateo
abstract
The Flysch di Solignano was deposited in a basin plain below the CCD close to the western margin of the Ligurian Tethys during Early Maastrichtian.The siliciclastic supply was mainly delivered by a crystalline basement of Sardinian-Corsican affinity. The carbonate supply, made up ofpelagic ooze, derived by oceanic intrabasinal structuralhighs represented by transform prisms uplifted within the compressive field affecting the Ligurian domain during Late Cretaceous. Resedimentation processes were likely triggeredby tsunami waves generated by high-magnitude earthquakes on this confined arm of the Ligurian Thethys.The hypothesis that resedimentation processes not only affected coeval pelagic ooze but also the underlying unconsolidated oceanic sediments of the Cretaceous oceanic coverComplessi di Base) is put forward.
1989
- The interaction of eustacy and tectonism fromprovenance studies of the Eocene Hecho Group TurbiditeComplex ( South-Centra Plyrenees Spain)
[Articolo su rivista]
Fontana, Daniela; G. G., Zuffa; E., Garzanti
abstract
Using a detailed etrographical procedure conceived for arenites rich in carbonate clasts,the influence of tectonism and eustacy on silicate/carbonate cycles of the Eocene Hecho TurbiditeComplex has been tested,and the palaeogeography of the source/basins ystemo utlined.Both extrabasinal and intrabasinal sources of sediments were active during basin f illing. Forelandt hrusting in the South Central Pyrenees has acted as the major control on the composition and architecture of the Hecho Turbidite Complex. Strong uplift of old silicate andcarbonate source terrains during southward thrust propagation was responsible for erosion, swamping and/or reduction of shelfal areas, and gave rise to siliciclastica nd carbonate basinalsequences.
1987
- Sedimentology, Petrografy and Provenance of the triassic Verrucano Group, Monte Argentario (Tuscany Italy)
[Articolo su rivista]
E. F., Mcbride; M. D., Picard; Fontana, Daniela; R., Gelmini
abstract
Deposition of the Verrucano Group (max. thickness 700 m) took place in a series of N-Strending grabens after rifting of the Hercynian basement. The presence of violet-gray mudrocks, caliche nodules and crusts, and the abundance of iron oxides in the sandstones and siltstones suggest that the Verrucano was deposited when the climate was semiarid.The scarcity of conglomerates and presence of upward-fining cycles suggest that the upper part was deposited by low-sinuosity mcandcring streams. T'he abundance ofconglomerate andabsenceo f sequencest ypic:rl of point bars indicate that the rest of the Verrucano was deposited chiefly by high-gradient braidcd streams. Low-grade metamorphism, which occurred duringthe Alpine orogcny, resulted in the recrystallization of argillaceous rock fragments and clay rip-up clasts, but did not clestroy primary sedimentary structures or recrystallize detrital quartz. Based on modal analyses, the sandstone composition in percents is quartz, ; microcrystalline quartz in rock fragments, quartz-mica rock fragments, mica rock fragments, iron oxides, Feldspars:The conglomerates are composed chiefly of quartz, showing various degrees of strain,and metachert .metasandstones, micas chist.
1986
- DIAGENESIS AND POROSITY EVOLUTION OF SUBMARINE-FAN ANDBASIN-PLAIN SANDSTONES. MARNOSO-ARENACEA FORMATION.NORTHERN APENNINES. ITALY
[Articolo su rivista]
Fontana, Daniela; E. F., Mcbride; R., Kugler
abstract
Sandstones of the Miocene Marnoso-arenacea Formation, a complex of slope, submarine-fan, and basin-plain deposits, were derived from several different Alpine and Apennine sources and have a remarkably diverse framework composition. Sandstones produce hydocarbons in the northern Apennines along the southern margin of the Po River valley. Reservoir quality is a function of both compaction, from burial load and tectonic compression, and cementation chiefly by ferroan calcite; secondary porosity is trivial in occurrence. The most severely compacted sands are those that: l) had the greatest quantity of clay matrix introduced either during slumping (chiefly proximal facies) or during other kinds ofdeposition (rare), 2) had the greatest quantity ofductile grains (claystone clasts,micas, some phyllite and schist grains), and 3) were deeply buried or compressed tectonically.Calcite in hemipelagic beds (up to 50%by weight) and locally as detrital grains provided a ready source of intraformationally derived cement. As a consequence, thin sands interbedded with mudstone and thick calcarenite beds, after compaction, became tightly cemented by ferroan calcite. Conversely, thick, stacked, channel-fill sands with minor carbonate detritus and few interbedded mudstones, however,avoided cementation and preserved modest primary porosity.Exploration in submarine-fan complexes similar in geometry and composition to the Marnoso-arenacea should be in the thick, stacked sandstones of channel-fill and lobe facies; turbidites rich in carbonate detritus, even if thick (> 3 m), are likely to have had all porosity occluded by cement.
1982
- Diagenetic provinces of the Verrucano Lombardo and Val Gardena sandstones (Permian), southern Alps, Italy.
[Articolo su rivista]
K. P., Helmold; Fontana, Daniela; R. G., Loucks
abstract
Diagenetic sequences and porosity in the arkosic and lithic Verrucano Lombardo and Val Gardena sandstones in N Italy are controlled dominantly by framework mineralogy and tectonic history. These stratigraphically equivalent Permian sandstones were deposited in various non-marine environments during an early stage of rifting at the base of the Alpidic cycle: they consist dominantly of quartz, feldspars and acidic to intermediate volcanic rock fragments. Source terrains consist of underlying Permian volcanic and terrigenous rocks of the pre-Permian crystalline basement. Three distinct diagenetic provinces have been differentiated, based on 1) the presence and nature of carbonate cement and/or replacement; 2) the presence of quartz cement; 3) the presence of kaolinization of detrital K-feldspar; and 4) the degree of recrystallization of the detrital clay matrix
1980
- Geochemistry of carbonate rocks and ferruginous horizons in the verrucano in southern Tuscany - paleoenvironmental and paleogeographic implications
[Articolo su rivista]
A., Annovi; Fontana, Daniela; R., Gelmini; C., Gorgoni; Sighinolfi, Giampaolo
abstract
Mineralogy and chemistry of carbonate rocks and of ferruginous shales and ironstones contained in the Permo(?)-Triassic continental sedimentary sequence from southern Tuscany (Italy) support detailed paleoenvironmental and paleoclimatic reconstructions. The composition of carbonate rocks rich in Mn and Ba and low in Sr is consistent with a marine tidal depositional environment of lagoonal type where high-Mg calcite deposition predominates and mildly evaporitic conditions favoured the formation of anorganic micritic limestones, sometimes containing minor amounts of evaporitic elements (Ba). The low Sr levels suggest post-depositional diagenetic processes in which fresh water acts as diagenizing solution. The ferruginous shales and ironstones seem to be related to the development of paleosoils under tropical weathering regimes favouring the selective mobilization of more soluble elements (Na, Ca) and of iron which reprecipitates near the soil surfaces according to the formation mechanism of the ironstone caps ("cuirasses ferrugineuses") in present tropical areas. A paleogeographic reconstruction of the Early- Middle Triassic environment of southern Tuscany is presented. The Verrucano sedimentary sequence was deposited in continental basins (graben) developed during a distensive phase after the Hercynian orogeny not far from the coast, under semi-arid conditions. The continental sedimentation was interrupted by limited marine ingressions during which coastal lagoons were established that were suitable for limited carbonate sedimentation.
1980
- Petrographic and sedimentological features of sandstones from Manciano, southern Tuscany
[Articolo su rivista]
Fontana, Daniela
abstract
Several Miocene sandstone slabs, outcropping in S Tuscany between the Albegna and Fiora rivers, have been studied. They are mostly coarse to medium-grained and well to moderately well sorted. The coarse to medium-grained sandstones are characterized by trough cross-bedding, generally with a dip of about 20-25o; burrows are rare. Fine grained sandstones, highly bioturbated, are interbedded with the coarser layers. The sedimentary structures, marine fossils, coarse grainsize and good sorting of these sandstones, show that they were deposited in high-energy conditions, probably in a barred shallow water environment.
1980
- Sediment dispersion and coastal evolution between Cape Spulico and Taranto during the Quaternary
[Articolo su rivista]
G. C., Parea; Fontana, Daniela; R., Valloni; A., Vinci
abstract
Beyond the present beach, 7 subsequent paleo-beaches terraced at various levels as far as more than 300 m towards the edge of the Apennines chain are recognizable. The present longshore drift, chiefly bound to the action of the winds from S and SE, moves the deposits from Capo Spulico and from Punta Rondinella toward the coast between the rivers Lenne and Patemisco. The longshore drift had the same trend in all the highest paleo-beaches, always keeping the same convergence zone between the rivers Lenne and Patemisco. The 'apenninic' extremity of each of the seven marine terraces has been uplifted with respect to the opposite extremity leant against the Apulia calcareous massif. - from English summary