United States

Flowing rivers represent the first vector of transport of sediments into the marine environment. With them, huge quantities of substances like nutrients, organic matter (DOC and POM), and chemical compounds are transferred. All these spread along the marine coastal system, where they can interact with benthic communities under different depositional processes, causing ecological shifts in their structure. To assess the influence of different depositional environments, trophic resources, and possible contamination by human activities on the large-scale distribution of prokaryotes, we investigated the variability of benthic prokaryotic communities (Bacteria and Archaea) in the surface sediments of the Middle and Southern Adriatic Sea, along the Italian coast. Results obtained through biochemical investigations show an environment reach in nutrients, with the trophic status much similar to that found in eutrophic environments. This was also confirmed from the prokaryotic diversity found, suggesting a strong role of the prokaryotic community in organic matter cycling. The large-scale microbial diversity dataset was correlated to different metadata and geochemical data to understand which factors affected the prokaryotic abundance and distribution and the organic matter load. Linear relationships between variables were present only for a limited range of values. Al2O3 and Fe2O3 concentrations in the sediments, grain size distribution, and distance from the coastline were identified as the major factors explaining the variation in the prokaryotic distribution in the surface sediment. These variables were associated in Adriatic sediments with the Alpine and Apennines river inputs and strongly correlated with deposits from the Po river, which suggest a strong influence in controlling the characteristics of the sediments distribution, trophic resources, and prokaryotic abundances. These observations implicate a strong influence on the function performed at the interface between water and sediments and the flux of nutrients to the entire benthic community.

SGI 2021

Benthic microbial community structure across the Adriatic sea and the role of terrigenous inputs

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L'Istituto Nazionale di Oceanografia e Geofisica Sperimentale - OGS e il Dipartimento di Matematica e Geoscienze dell'Università di Trieste sono orgogliosi di ospitare il 90° Congresso della Società Geologica Italiana a Trieste dal 14 al 16 settembre 2021. La modalità del congresso è interamente online.

Con il motto "Geologia senza frontiere" questo evento mira a promuovere le Scienze della Terra come disciplina scientifica proiettata nel futuro, oltre i confini geografici, politici e disciplinari, per comprendere meglio l'interno del Pianeta Terra e la struttura del sottosuolo, difendere la società da pericolosi eventi geologici, comprendere meglio la variabilità climatica, pianificare l'utilizzo delle georisorse in modo etico e nel rispetto dell'ambiente.


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The National Institute of Oceanography and Experimental Geophysics - OGS and the Department of Mathematics and Geosciences of the University of Trieste are proud to host the 90th Congress of the Italian Geological Society in Trieste on 14-16 September 2021.  The Congress will be held entirely online.

With the motto "Geology Without Borders" this event aims to promote Earth Sciences as a scientific discipline projected into the future, beyond geographical, political and disciplinary boundaries, to better understand the interior of Planet Earth and the structure of the subsurface, defend society from dangerous geological events, better understand climatic variability, plan the use of geo-resources in an ethical way and respecting the environment.


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Earth Sciences should be understood not only as necessary for a better understanding of the interior of the planet Earth, but also as a defense of society from dangerous geological events, for the understanding of climatic variations, for the planning and use of georesources in a ethical and respecting and protecting the environment.

technical paper

A large Neogenic "Calcari a Lucina" deposit - i.e. hydrocarbons-rich cold seep carbonate -, reaching 40 m of thickness and several tens of meters of extension, crops out in the Crotone Basin (South Italy). It is composed of authigenic carbonate forming a facies referable to the conduits of gas/fluid, crosscutting early carbonate-cemented bioclastic and siliciclastic sediments definable as pavement facies. Conduits are commonly characterized by the accretion of meters thick thinly laminated and banded calcite and formed by the alternation of dark micritic laminae and clear crystalline layers. The micritic laminae are characterized by an autochthonous microbial peloidal to dendrolitic fabric, incorporating coprolites and planktonic foraminifera. In contrast the crystalline layers are characterized by microspar laminae and centimeters thick sparry crusts composed of prismatic zoned calcite crystals. The pavement facies is typified by foraminiferal bioturbated mudstone/wackestone gradually passing to mixed arenites as the increasing of the siliciclastic grains composed of quartz, plagioclase, phyllosilicates, aphanitic lithic grains, phaneritic rock fragments, and heavy minerals, all immersed into a micritic carbonate matrix, and indicating both sedimentary and crystalline basement source. The foraminiferal assemblage, characterized by almost exclusively by planktonic forms, and the relative proportion of sandy/silty grains, indicate a deep-water setting with occasional siliciclastic coarser sedimentary flows. A common chemosynthetic macrofauna composed of often articulated and in life-position Lucinids, Mytilids and Vesicomids bivalves, associated to tubeworms and gastropods, is commonly present into such sediments. The deposits of the pavement facies are commonly brecciated, possibly because the overpressure conditions established by the gas/fluid injection, and the displacive growth of the conduit deposits that crosscut the sediments, suggesting a very early cementation of the micritic matrix. Clasts of breccias are also later lined by primary fibrous to acicular isopachous to fan-shaped calcite cement. The high diversity of the heavy minerals in the mixed arenite deposits together with the presence of unstable (green amphibole) and moderately stable (epidote, garnet, sillimanite) heavy detrital species, indicates a burial depth comprised between 600 m and 2000 m during which a late diagenetic phase occurred. A pervasive neomorphic recrystallization of the carbonate grains and the precipitation of mosaic equant calcite cements, filling the remnant voids, took place during this phase.

Neogene seepage carbonate deposition in the Crotone Basin (South Italy), preliminary results

In Late Triassic-Early Jurassic time, across one of the major extinction event of the Phanerozoic, the Western Tethys was affected by climatic and environmental changes followed by extensional tectonics related to the opening of the Alpine Tethys. The Norian-Upper Jurassic successions of the eastern Northern Calcareous Alps (Stumpfmauer, Austria), exposed in the Königsberg and Oisberg synclines show the transition from the early dolomitized peritidal facies of the Norian Hauptdolomit to the Rhaetian limestone-siliciclastic succession of the Kössen Formation. 34 facies have been characterized in the succession, composing eight distinct superimposed sedimentary units labelled from A to H, from base to top. Peritidal facies organized in shallowing-upward cycles capped by subaerial exposure and overlain by claystone beds characterize Unit A. Unit B is associated with fossiliferous claystone and marlstone attesting for open marine subtidal conditions developed below the effective wave base. The frequent siliciclastic input affecting Unit B records a shift from arid to humid climatic conditions. Unit C facies association defines a continuous coral limestone bed representing a regional marker developed in a low-energy setting with reduced siliciclastic input. Unit D, marking a renewed clay input, is characterized by skeletal peloidal packstone/wackestone and coated-grain grainstone forming subtidal shallowing-upward cycles capped by subaerial exposures, representative of open marine subtidal conditions affected by high-frequency sea-level changes. Unit E starts with a basal transgressive lag with crinoidal lithoclastic rudstone overlain by progradational cross-bedded coated grain-ooidal grainstone with quartz, developed in a high-energy inner ramp setting: The disappearance of bioclasts suggests that this unit may reflect the T-J biotic crisis. A sharp change in deposition characterizes Unit F with bivalve and ostracod wackestone/floatstone overlain by microbial boundstone with Cayeuxia associated with peloidal packstone/grainstone. This facies association is indicative of low-energy deep water conditions passing toward the top to shallow-water setting with moderate energy conditions related to subtidal lagoonal environments. Unit G consists of cross-laminated crinoidal coated grain grainstone and spiculite developed in a relatively deep-water shelf setting affected by detrital quartz siliciclastic input. Unit H records the definitive drowning of the shelf: it consists of red crinoidal, thin-shelled bivalves packstone/rudstone with cephalopods and radiolaria wackestone attesting for a deep pelagic environment.  The observed stratigraphic setting can be framed in the regional evolution of the Western Tethys and can be traced from the Western Carpathians to Southern Alps suggesting coherent environmental changes and stratigraphic evolution, documenting the role played by climate and tectonics on sedimentation at regional scale.

Facies analysis and paleoenvironmental evolution of the Norian-Jurassic sedimentary successions of the Northern Calcareous Alps (Stumpfmauer-Austria)

Being at the boundary between marine and continental realms, marine caves are affected by wide environmental variability for the interaction of marine and continental waters; for this, they are natural laboratories for studying the effects of seasonal and long-term environmental variability also in the perspective of global changes. The first studies of benthic foraminifera from marine caves of the Mediterranean Sea have been carried out in the Gulf of Orosei in the context of a scientific project which started in 2014 and has continued to this day. They demonstrated that benthic foraminifera are very sensitive environmental proxies in these habitats, due to their high diversity and adaptability. The Bue Marino system is constituted by North, Middle and South Branch which join together close to the coast. The study of benthic foraminifera and sediment texture from surface samples, associated with parameters of bottom water, indicated that the Middle Branch was characterized by warmer, saltier and less oxygenated water than the rest of the cave, and by finer sediment with abundant vegetal debris, probably supplied from the mainland during strongly rainy periods (Romano et al., 2021). Then, it was reasonable hypothesizing that cave sediments, although deposited in enclosed environment, are reliable archives of past climatic changes. A 18 cm long sediment core, collected in 2018 in the Middle Branch, was studied for grainsize and benthic foraminifera in order to highlight evidence of temporal changes of environmental conditions and their causes. In the whole core, sediment texture was homogeneous, with prevailing sand and silt in similar proportions, while clay was less abundant and gravel nearly absent. Two hyaline (Ammonia inflata and A. tepida) and one agglutinated species (Eggerelloides advenus), dominated the assemblage, accounting for a total of 70-92%. A main change occurred along the core, at 11 cm depth, for the shift from an assemblage in the lower section with prevailing A. inflata, to another one where the highly opportunistic E. advenus and A. tepida dominated. Of these two assemblages, the latter was more similar to that recorded in the surface sample (0-2 cm), collected at the same sampling station, for the dominance of E. advenus, despite A. inflata slightly prevailed on A. tepida. It was interpreted as the result of a highly organically-enriched environment where opportunistic taxa benefited of abundant degraded organic material under low-oxygen conditions. The prevalence of the “indifferent” A. inflata in the lower core suggests less stressed conditions with minor supply of continental vegetal debris, probably due to less frequent and/or intense rainy episodes in past times.

Paleoecological reconstruction and modern analogues from foraminiferal proxies in the Middle Branch of Bue Marino Cave (Sardinia, Italy). Work in progress

Cold seep environments are often associated with chemosynthetic communities at the seafloor, reflecting the spatial distribution and magnitude of methane fluxes in the sediment underneath. Quantifying areal fluxes and rates of consumption via anaerobic oxidation of methane (AOM) is extremely important for better understanding the future response of the benthic filter to climate-induced ocean warming. Short-time-scale transient processes such as tides, seasonal bottom water temperature fluctuations are efficiently recorded in unsteady-state pore water profiles. However, to interpret the long-term trends in methane fluxes and controlling factors one needs to integrate this data with sedimentary proxies and conduct paleo-reconstructions. We present a case study from the SW Barents Sea at Leirdjupet Fault Complex, where active methane seepage has been observed in summer 2018 from 295 m to 350 m water depth and is associated with microbial mats and tubeworms. We discuss the modern seepage conditions based on pore water data and habitat maps generated through Object-Based Image Analysis (OBIA) classification, and discuss the history of seepage recorded in sediment cores. A new ROV survey conducted in June 2021 in the same area revealed a very different situation compared to 2018, consistent with the long-term reconstructions since Late Weichselian deglaciation.

Every cold seep tells a story: the case study of Leirdjupet Fault Complex, SW Barents Sea

The Mississippian Derbyshire Carbonate Platform outcrops, in the Peak District in UK, host many mud mound complexes (Gutteridge, 1995). The one near the village of Monyash, in Ricklow Quarry, is one of the best for outcrop quality and accessibility. Fieldwork and petrographic study allowed recognising three facies associations in the complex. A basal tabular portion, five metres thick, consists of nodular packstone-rudstone beds with patches of clotted peloidal-leiolitic micrite boundstone, interbedded with tabular clotted peloidal-leiolitic micrite/fenestellid bryozoan boundstone mounds (FA 1). The overlying, dome-shaped, decametre-size mound complex core formed by lateral accretion of numerous dome-shaped, metre-size mounds. These consist of an association of fenestellid bryozoan/clotted peloidal-leiolitic micrite boundstone with radiaxial fibrous calcite cement (FA 2). The mound core is flanked by dipping beds characterized by clotted peloidal-leiolitic micrite/fenestellid bryozoan boundstone, passing downslope to skeletal packstone with brachiopods and crinoids (FA 3). Flank beds are transitional to the crinoid-rich packstone/grainstone-rudstone beds occurring laterally to the mound complex. Clotted peloidal-leiolitic micrite textures have been interpreted as originated from in-situ precipitation mediated by the presence of microbial mats on the sea floor (Pickard, 1996). Likely, the complex developed during a deepening of the depositional environment in a middle-ramp intraplatform setting, by microbial communities colonisation of the seafloor. Microbially-mediated in-situ precipitates were then occupied by brachiopods and bryozoans, forming mounds whose vertical growth was prevented by currents (FA 1). A further deepening of the environment allowed vertical growth and coalescence of dome-shaped mounds, which accreted to form the decametre-size core (FA 2). Flank beds (FA 3) developed as a result of the metre-scale mound complex core relief over the seafloor. The presence of inner ramp crinoidal grainstone beds onlapping the complex core and vadose cements on top of the mound complex reveal that mound growth was interrupted by a phase of relative sea-level fall and subaerial exposure. Preliminary evaluation of the diagenetic history through petrographic analysis shows a first phase of marine diagenesis (radiaxial fibrous calcite cement), followed by meteoric diagenesis (dissolution vugs, pendant vadose cement). During the following burial phase, mechanical compaction, cementation (blocky calcite cement), silicification and pressure solution occurred. Fissure formation was followed by precipitation of coarse late calcite cement. Finally, hydrocarbons and mineralising fluids pumped from adjacent basinal areas (e.g. Walkden & Williams, 1991) opened fractures, stylolites and intercrystalline discontinuities. Presence of bitumen in the resulting fissures prevented the precipitation of further calcite cement, leaving open secondary porosity.

Facies architecture and diagenesis in a Mississippian mud mound complex from Derbyshire (UK)

The Monte Cocuzzo tectonic window, located in the central part of the Catena Costiera Calabra (Calabria - south Italy), hosts a thick Norian-Rhaetian carbonate succession characterized by three different depositional units representing three successive carbonate platform systems of the western Tethys realm: early-middle Norian Lower Complex, middle-late Norian Intermediate Complex and late Norian-Rhaetian Upper Complex. The Lower Complex platform system is characterized by spread and isolated bio-constructed bodies showing an oligotypic community with a primary framework composed by sponges, red algae and corals; and a secondary framework by microbialites, foraminifera and serpulids. Globose clusters of sponges (Olangocoeliidae), encrusting red algae (Solenopora) and microbial crusts, represent the start-phase of the reef construction. In the successive frame-building phase, sponges and red algae progressively decrease in favor of pennulate isolate (Distichophyllia sp.) and colonial (Retiophyllia sp.) corals, the latter forming dendroid fun-shaped tufts (50-60 cm thick). Coral skeletons are encrusted by microbial laminae, serpulids and red algae and are immersed into bioclastic detritus composed by echinoid fragments, bivalves and gastropods tests and rare bryozoans. The primary framework is composed by 41% sponges, 35% red algae and 24% corals, whereas the secondary framework by 41% foraminifera, 35% microbialites and 24% serpulids. The accessory organisms are 19% echinoids, 8% bivalves and 6% gastropods and the rest of the volume is represented by non-bioclastic sediments (39%) and primary cements (28%). The bioconstructions are commonly onlapped by bioclastic packstone-grainstones enriched into dasycladacean algae and foraminifera indicating a relatively shallow water environment, probably characterized by disphotic and eutrophic waters as testified by the presence of pennulate corals. These bioconstructions can represent patch reefs located along the carbonate platform margins directly facing an internal restricted basin generally characterized by stressed environmental conditions. In fact, during the whole Norian, syn-depositional down-faulting pulses, accompanied by gradual eustatic sea-level drops, induced repeated episodes of basin restrictions with a consequent limited water circulation and stressed conditions affecting the late Triassic Western Tethyan general carbonate platform domain.

Palaeoecology of late Triassic bioconstructions in the Western Tethyan domain (M.te Cocuzzo - North Calabria)

Classic paleogeographic scenarios for the Cretaceous of the Central Mediterranean area depicted the peri-Adriatic region as punctuated by patchy carbonate platforms far from the main emergent lands. The increasing dinosaur record of African affinity in Italy questioned such palaeogeographic scenarios and suggests the proximity of landmass areas connecting Africa and Adria during Cretaceous times. Besides several track-sites and some exceptionally-preserved specimens, the Italian dinosaur record also consists of isolated bones, among which the fragment of a theropod bone discovered in NW Sicily (Capaci) in a carbonate succession pertaining to the Panormide Carbonate Platform (PCP). This bone fragment was previously referred to the Cenomanian and its occurrence strongly supports the hypothesis of a land bridge connecting Africa and Adria via PCP. More recently, new sedimentological and biostratigraphic data from this carbonate succession (i.e. Pizzo Muletta) have allowed to predate the chronostratigraphic position of the dinosaur bone to upper Aptian–lower Albian and to assess a detailed Aptian–Cenomanian evolution of this sector of the PCP. In particular, a karstic overprint has been observed thus indicating a subaerial exposure of the platform preceding its drowning in latest Cenomanian times. The obtained results extend the chronostratigraphic interval of the possible land bridge between Africa and Adria at least from Aptian to Cenomanian and highlight the progressive tectonic dismantling of this connection during the Late Cretaceous. 

The continental bridge between Africa and Adria: new insights from the Lower Cretaceous of NW Sicily (Italy)

The Calcare di Base (CdB) Fm is a carbonate/evaporitic unit formed during the onset of the Messinian Salinity Crisis in the the central Mediterranean region, before the deposition of massive halite and sulphate bodies. An integrated facies and stratigraphic analysis of the CdB was performed along the neogenic basins of north Calabria, that allowed to propose a sedimentary and evolutionary model in which the CdB consists of a carbonate, with minor evaporites, platform-to-slope system, formed during a general cold and arid climate period, characterized by precession-forced more humid intervals. The inner platform setting was generally characterized by a sabkha-type environment with scattered lakes and coastal lagoons grading into a shallow-marine unrimmed shelf. In particular, as the general aridity, restricted conditions frequently established, inducing hypersalinity and local anoxia. Such general stressed environmental conditions favored the thriving of extensive lithifying microbial-mats dominated by sulfur bacteria, that acted as the main carbonate factory along the whole shelf, producing widespread microbial carbonate deposits, associated with precipitation of gypsum-dominated evaporitic deposits. During the more humid periods an increasing in the runoff provoked the substantial reduction of the carbonate production, the interruption of the evaporitic sedimentation, the input of fine to coarse silicilcastic sediments, and the formation of dissolution breccias. The slope setting is inferred with a general low-angle profile and was typified by breccias and disorganized floatbreccias commonly developing along the inner slope, and by slides, slumps and channelized turbidites forming along the mid-to-outer slope to basin. During the arid periods the resedimentation processes were generally limited and characterized by monomictic (carbonate) debrites. In comparison, during the humid phases, the enhanced erosion and the consequent mixed carbonate/evaporite/terrigenous sediment exportation towards the basin, resulted in the formation of thicker polymictic breccia and megabreccia bodies.

The Messinian pre-salt carbonate/evaporite platform system of the Central Mediterranean (Calcare di Base Fm - North Calabria)

Several Neogene-Quaternary basins in central-western Italy host travertine deposits and are influenced by extensional and strike-slip tectonic activity. These continental carbonate deposits are principally related to hydrothermal fluids circulating and emerging onto the surface along fractured carbonate bedrocks or discontinuities. The Acque Albule Basin (Tivoli, Central Italy) is a tectonically-controlled depression hosting the Pleistocene Lapis Tiburtinus travertine. The 3D modelling permits to reconstruct the geometry and architecture of the geobodies filling the sedimentary basin and its evolution. The reconstruction of the different surfaces bounding the travertine geobodies of the Lapis Tiburtinus highlights a complex scenario mainly characterized by depression and relief morphological elements, associated with subaqueous, palustrine, slope and channel depositional environments. The results obtained by the 3D modelling of the quarried area of the Lapis Tiburtinus travertine deposits and the spatial distribution of discontinuity surfaces and geobody architectures provide information on the factors influencing the sedimentary filling of the Acque Albule Basin. The presence of E-W oriented lens-shaped geometries laterally migrating reveals a drainage system persistent through time toward the southern part of the study area in the direction of the Aniene River, bordering the Acque Albule Basin in the South. The travertine deposits related to the Lapis Tiburtinus developed in an area of 28 km2 and accumulated in a system of sub-basins, each 1-2 km2 wide, mainly characterized by subaqueous conditions and interconnected by a hydrographic network related to the Aniene River. The results obtained reveal that tectonic activity was the main control on the evolution of the Acque Albule Basin over a time-scale of hundreds of thousands to million years, influencing the basinal subsidence through time and the locations of active hydrothermal springs precipitating the travertine. However, climatic changes govern rainfall precipitation rates and groundwater level affecting spring discharge and travertine deposition rate. Glacio-eustatic oscillations linked to the climatic fluctuations of the last 115 kyrs controlling the Aniene River base level have influenced the depositional setting and the geometry and architecture of travertine geobodies.

Climatic and sea-level changes control travertine deposition: the Lapis Tiburtinus case study (Tivoli, Central Italy)

The Messinian salinity crisis (MSC) was a geological event characterized by the deposition of huge volumes of evaporites in the Mediterranean basin. After decades of scientific debate, the consensus model (CIESM, 2008) proposed a new stratigraphic framework, and the MSC was subdivided in three stages (Manzi et al., 2013; Roveri et al., 2014). Stage 3 started at around 5.53 Ma, and its uppermost part corresponds to the “Lago-Mare” phase, characterized by the occurrence of brackish shallow water ostracods of Parathetyan origin. These deposits are sharply overlain by Zanclean open marine fine-grained sediments recording the establishment of open marine condition at the end of the MSC at 5.33 Ma. The interpretation of such abrupt transition is debated: it could be a catastrophic reflooding of the Mediterranean according to some authors or a gradual refilling of the basin according to others. In many Mediterranean sections, the Messinian-Zanclean boundary is marked by a poorly investigated dark layer (DL), that can provide insights on the mechanism responsible for the refilling of the Mediterranean at the end of the MSC. We investigated DL in six sections along a W to E transect of the Apenninic foredeep trough an integrated micropaleontological, petrographic and ichnological approach. Preliminary results show that, although the texture, structure, and lithological composition of the DL change from section to section, this is always interbedded between the uppermost Lago Mare and the basal Zanclean sediments through a sharp and conformable boundary, arguing against a catastrophic refilling of the Mediterranean. Moreover, the DL is strongly bioturbated, with crypto and large burrows filled with Pliocene basal mud (Reticulofenesta zancleana), which suggests starved condition at early Zanclean. Finally, the preliminary results on the association of benthic foraminifera and on the P/B ratio, indicate a gradual increase in bottom oxygen content and in depth from the top of the DL to the lowermost Pliocene.

Benthic microbial community structure across the Adriatic sea and the role of terrigenous inputs

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Neogene seepage carbonate deposition in the Crotone Basin (South Italy), preliminary results

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Benthic microbial community structure across the Adriatic sea and the role of terrigenous inputs

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Neogene seepage carbonate deposition in the Crotone Basin (South Italy), preliminary results

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Karst morphologies and related risks in gypsum of Monferrato area (NW Italy)

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