United States

The Mediterranean is a semi-enclosed sea formed by two sub-basins, the eastern Mediterranean (E-Med) and the western Mediterranean (W-Med), connected through the Strait of Sicily. Four main deep-water convection cells fuel the Thermohaline circulation of the Mediterranean (Med-THC). In the E-Med, deep water is formed in the Adriatic Sea and the Aegean Sea, while an intermediate-water is formed in the Levantine Sea (Levantine Intermediate Water, LIW). The Western Mediterranean Deep Water is formed in the Gulf of Lions. Since all cells are interconnected, variations in one cell could be transferred to the others by modifying the Med-THC. The present study focuses on the analysis of the sediment core NDT-6-2016 at the west flank of Sicily channel, recovered at 1066 m of water depth, which is nowadays located bellow the interphase layer between the eastern and western originated water-masses. Therefore, this location is suitable for exploring changes in the inter-basin water exchange along the last 15 kyr cal. BP. Nd isotopes measured in planktic foraminifera coatings allow estimating changes in the export rates of the eastern Mediterranean source-water (ESW) masses underlying the occurrence of two anomalous events: The Younger Dryas characterized by an outflowing excess of ESW and the last sapropel (S1) with opposite circumstances. The export rates of EMS waters are estimated to have been up to three times higher during the YD than during the S1. These results are discussed in the context of other geochemical, sedimentological and micropaleontological proxies that allow us to have a more complete picture of the oceanographic changes associated to these events of Med-THC major reorganization.

SGI 2021

Water-Masses exchange through the Straitof Sicily during the Last Deglacial and Early Holocene

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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.


**Please note, times listed in the SCHEDULE tab (calendar icon) reflect YOUR LOCAL TIME ZONE. The main timezone for this conference will be Central European Summer Time.**

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.

poster

Over the last few decades, different researches have led to important advances in our understanding of late Quaternary Antarctic Ice Sheet (AIS) behavior. However, the continental shelf margin remains still poorly investigated. To address this issue, we aim to increase the knowledge of the last glacial/deglacial dynamics in the Central Basin (slope-basin system) using a multidisciplinary approach, including sedimentological, micropaleontological, and tephrochronological analyses performed on marine sediments cores. Based on grain size clustering and the sortable silt data, together with diatom, silicoflagellate and foraminifera assemblages, we recognize three stratigraphic units. Unit 1 (24-17 ka BP) documents the influence of the ice shelf calving zone vicinity, Unit 2 (17-10.2 ka BP) represents the progressive retreat of the ice shelf due to Circumpolar Deep Water inflow, and Unit 3 (10.2 ka BP-present) corresponds to the establishment of seasonal sea ice with a strengthening of bottom currents. The dominant and persistent process is the sedimentation controlled by contour currents, which tend to modulate intensity in time and space. The study also allowed us to document the presence of a primary volcanic ash layer dated 22 ka BP correlated with the explosive activity of Mount Rittmann. This study has been conducted in the framework of the STREAM Project (Late Quaternary evolution of the ocean-ice sheet interactions: the record from the Ross Sea continental margin, Antarctica) funded by the Italian Ministry of Foreign Affairs and International Cooperation and the National Research Foundation of Korea.

Environmental and Oceanographic Conditions at the Continental Margin of the Central Basin, Northwestern Ross Sea (Antarctica) since Last Glacial Maximum

In this paper we analyze how oceanic circulation affects sediment deposition along a sector of the Ross Sea continental margin, between the Iselin Bank and the Hillary Canyon, and how these processes evolved since the Late Miocene. The Hillary Canyon is one of the few places around the Antarctic continental margin where the dense waters produced onto the continental shelf, mainly through brine rejection related to sea ice production, flow down the continental slope and reach the deep oceanic bottom layer (Gales et al., 2021). At the same time the Hillary Canyon represents a pathway for relatively warm waters, normally flowing along the continental slope within the Antarctic Slope Current, to reach the continental shelf. The intrusion of warm waters onto the continental shelf produces basal melting of the ice shelves, reduces their buttressing effect and triggers instabilities of the ice sheet that represents one of the main uncertainties in future sea level projections. For this study we use seismic, morpho-bathymetric and oceanographic data acquired in 2017 by the R/V OGS Explora. Age models from two drilling sites (U1523 and U1524) of the Integrated Ocean Discovery Program (IODP) Expedition 374 (McKay et al., 2019). Oceanographic data, together with a regional oceanographic model, are used to support our reconstruction by showing the present-day oceanographic influence on sediment deposition. Regional correlation of the main seismic unconformities allows us to identify eight seismic sequences. Seismic profiles and multibeam bathymetry show a strong influence of bottom current activity on sediment deposition since the Early Miocene and a reduction in their intensity during the mid-Pliocene Warm Period. Oceanographic data and modelling provide evidence that the bottom currents are related to the dense waters produced on the Ross Sea continental shelf and flowing out through the Hillary Canyon. The presence of extensive mass transport deposits and detachment scarps indicate that also mass wasting participates in sediment transport. Through this integrated approach we regard the area between the Iselin Bank and the Hillary Canyon as a Contourite Depositional System (ODYSSEA CDS) that offers a record of oceanographic and sedimentary conditions in a unique setting. The hypotheses presented in this work are intended to serve as a framework for future reconstructions based on detailed integration of lithological, paleontological, geochemical and petrophysical data.

Bottom current control on sediment deposition between the Iselin Bank and the Hillary Canyon (Antarctica) since the late Miocene: an integrated seismic-oceanographic approach

The Cenomanian–Turonian Oceanic Anoxic Event 2 (OAE-2) represents a major perturbation of the global carbon cycle associated with the extensive deposition of organic carbon-rich deposits (black shales) in the oceanic basins, worldwide. Numerous studies have suggested that enhanced volcanic activity at mid-oceanic ridges and large igneous province (LIP) eruptions may have acted as potential trigger mechanisms of this event. These phenomena caused excess CO2 degassing and a consequent dramatic temperature increase in the oceans and atmosphere. Although the geochemical, sedimentological and paleontological changes throughout the OAE-2 are well-known in basinal deposits, the shallow- water carbonate counterpart is still poorly investigated. The OAE-2, however, strongly impacted both deep and shallow-water ecosystems. The limited information on the expression of the OAE-2 in carbonate platforms represents a critical gap in our understanding of ecological responses to abrupt paleoenvironmental/paleoclimatic changes in the mid-Cretaceous, given that shallow shelves accounted for a significant part of the global ocean biological productivity and carbonate production. In this work we present new high-resolution geochemical and sedimentological data across the OAE-2, based on bivalve shells and bulk rock material from a well exposed upper Cenomanian – lower Turonian section, in the carbonate successions of the Friuli Carbonate Platform (FCP) cropping out in the Karst area, near the city of Gorizia. Biostratigraphy and carbon-isotope stratigraphy were used to establish a precise stratigraphic dating and for high resolution correlations with coeval shallow-water and reference open-ocean sections. Sr-isotope data, Hg concentration and other geochemical proxies have been used to highlight possible evidence of volcanic activity and changes in weathering and to evaluate paleoenvironmental conditions on the FCP during the OAE-2. Results highlight that, during the event, the FCP underwent major biotic and geochemical changes that these fluctuations can be compared to those occurring in coeval carbonate platforms of the Tethys during the OAE-2. 

First evidence of the Oceanic Anoxic Event -2 in the shallow-water carbonates of the Friuli Carbonate Platform: geochemical and sedimentological data

Here we present an integrated calcareous plankton and geochemical record from the Tethyan Terche and Madeago sections (NE Italy), deposited in a middle-lower bathyal setting. These sections record a negative Carbon Isotope Excursion corresponding to Eocene Thermal Maximum 2 (ETM2, ~54 Ma). Our planktic foraminiferal and calcareous nannofossil records show significant, though temporary, changes in both sections across this event. No significant dissolution occurred that could have affected the assemblages. Warm index surface-dweller Acarinina increased while of the deeper-dweller chiloguembelinids and subbotinids declined in abundance. A test reduction of up to 50% compared to pre-event sizes for both surface- and deeper dwellers planktic foraminiferal is particularly marked at Madeago. While symbiont bleaching can reduce growth, both symbiont and asymbiotic planktic foraminifers were affected at the same scale in our sections at the ETM2, and hence not a likely cause of the size reduction. The enhanced surface remineralization of organic matter due to warming may have reduced the food input at the thermocline, thus contracting the deeper ecological niches. The calcareous nannofossil assemblages provide evidence of increased surface water eutrophy during the ETM2. The increase in small placoliths Toweius and Ericsonia may indicate that dwarfism also affected nannofossil assemblages, though to a lesser degree. We thus hypothesize that the ETM2 perturbation impacted the entire upper water column possibly changing stratification and niche spaces. To establish whether the observed dwarfism was related to environmental stressors which are not commonly linked to the ETM2 climatic perturbation, we quantified the Hg (ppb), TOC (wt%) and Hg/TOC (ppb/wt%) geochemical proxies through our sections. Results show an increase in Hg in both sections at the base of the ETM2. We attribute this increase to coeval submarine igneous events that might have introduced biolimiting metals, which changed plankton productivity and possibly affected test size. However, we cannot exclude reworking of the metal because we record an increase in sedimentation rate and nannofossil rework at the ETM2. We suggest that the plankton dwarfism, here documented for the first time across the ETM2, could be the result of the coupled effect of increase in biolimiting metals and changes in the physicochemical structure of the upper water column.

Evidence of Tethyan calcareous plankton dwarfism across the ETM2

We present here data on changes in Mg/Ca derived paleotemperatures from the southern Atlantic Site 1263 across the Early Eocene Climatic Optimum (EECO; ~53-49 Ma). The EECO, that records the peak of Cenozoic warmth, and possibly of the CO2 pressure (e.g., Zachos et al., 2001, Sciences; Anagnostou et al. 2016, Nature Inglis et al., 2020 Clim. Past), induced climatic and paleoceaographic changes that significantly impacted planktic foraminferal assemblages. The main change, recorded form several sites (Atlantic and Pacific Oceans, Tethys) is the permanent and markedly declined in abundance and diversity of the mixed-layer dwelling symbiotic bearing genus Morozovella coupled with the increase of genus Acarinina (Luciani et al., 2016; Luciani et al. 2017a; Luciani et al. 2017b; D’Onofrio et al., 2020). This decline occurred at the EECO beginning, close to the carbonate isotope excursion known as ‘J event’ (~53 Ma). In addition, a reduction in morozovellid test-size occurred across EECO as recorded from Atlantic ODP sites 1051, 1258 and 1263. Several potential stressors may explain both the reduced size and the permanent morozovellid decline. These include algal photosymbiont inhibition (bleaching), increase in temperature, decrease in pH and/or calcite saturation state. Even though a bleaching test at Site 1051 revealed only a transient reduction of algal-symbiont relationships just after the morozovellid abundance decline (Luciani et al., 2017a), a general reduction in δ13C gradient (~ 0.5 ‰) between morozovellids and the thermocline dweller Subbotina spp. through the EECO is recorded from the Atlantic sites. This suggests that the former group became less reliant on photosymbionts and/or may have moved to slightly deeper depth in the mixed-layer. Even though a link with the EECO perturbation is evident, the driving causes of the recorded modifications are still unknown. Detailed paleotemperatures across the observed changes were lacking. We therefore obtained Mg/Ca derived paleotemperatures from Site 1263 through Laser Ablation, a method widely applied. Preliminary Mg/Ca data reveal that Morozovella crater and M. subbotinae record a major warming across EECO greater than that of Acarinina coalingensis and A. soldadoensis.Although the exact causes of photosymbiont bleaching can be manifold, increased temperature is considered a primary cause of bleaching in present tropical larger benthic foraminifera (e.g., Hallock, 2000). The higher rise in temperature recorded by morozovellid may explain the reduced symbiotic relationship and suggests one possible reason for their reduction in abundance and size, even though other potential stressor such as pH decrease should be explored. We record from Site 1263 also a temperature increase at the thermocline that may be one of the causes explaining the drop in abundance of subbotinids and chiloguembelinids at the EECO. 

Mg/Ca Paleotempertures changes at the demise of plankic foraminiferal genus Morozovella across the Early Eocene Climatic Optimum  (Site 1263, Southern Atlantic Ocean)

The genus Xenophora comprises species of marine gastropods, known from the Cretaceous and still living today, which have the ability to form their shells agglutinating objects with different origins, from other shells to bio- or lithoclasts. Different agglutination potentials are shown by species of Xenophora, from species lacking attachments to others completely covered, as the case of the Mediterranean Xenophora crispa (König, 1825). Shell sections of fossil (Early Pleistocene, Arda and Stirone Rivers, Italy) and recent specimens (Mediterranean Sea, Spain) of X. crispa were here analyzed at the Scanning Electron Microscope (SEM) and powders, collected from different parts of the shell, at X-Ray Diffraction (XRD), in order to characterize in detail the microstructure and the mechanisms, function and behaviour of the agglutination in the same species through time, in this case over about 2 millions of years. Also, as the Arda and Stirone River sections were deposited during the Early Pleistocene, this research allows to examine if and how these parameters varied during a climate change. Indeed, the Early Pleistocene was a time interval characterized by several climatic oscillations linked to glacial/interglacial cycles and the Mediterranean area was strongly affected by these climatic changes showing in marine environment a progressive climatic cooling. This study shows that the functional purpose of the agglutination in X. crispa may be related to a snowshoe strategy to successfully colonize muddy substrates, coupled with tactile and olfactory camouflage. Indeed, this species secretes in the columella and peripheral edge of both fossil and recent specimens a less dense and a more organic rich calcitic fabric, possibly to lighten the shell thickest parts in order not to sink in soft sediments and to facilitate the shell raising from the substrate to create a protected feeding area. This behaviour and the shell microstructure seem to have been maintained by X. crispa over 2 My time span, thus allowing to suppose that this species did not suffer the climatic cooling of the Early Pleistocene.

From the Early Pleistocene to the Recent: how is Xenophora crispa biomineralization varied?

The increasing effects of anthropogenic carbon dioxide (CO2) emissions on climate change pressure the scientific community to provide accurate predictions of the future consequences of these variations. The oceans and marine organisms are strongly affected by climate and CO2atm, but they also produce pivotal feedback on climate. Thus, studying the marine carbon cycle is crucial to understand the drivers regulating the past, present, and future evolution of climate. Among marine biota, coccolithophores, a group of calcifying marine phytoplankton, play a key role in the ocean carbon cycle at various timescales providing pivotal information on the oceans’ capacity towards CO2 buffering. They are also particularly sensitive to environmental variations making them excellent climate proxies. In this study, experimental cultures of the species Helicosphaera carteri cultivated in turbidostats under CO2-controlled conditions were compared to the fossil coccolithophore assemblage at the International Ocean Discovery Program (IODP) Site U1501 (South China Sea). The combination of paleontological and culture-derived data can improve predictions of the state of biodiversity in the future under varying climate change scenarios. Helicosphaera carteri cultures were grown under 425 ppm CO2, a level consistent with the best-case scenario predicted by the Intergovernmental Panel on Climate Change (IPCC), the Representative Concentration Pathway (RCP) 2.6 (IPCC, 2014). The selected time interval for studying the fossil coccolithophore assemblage belongs to Marine Isotope Stage 5 (130-70 kyr), a geological interval considered as an analogue for modern warming. Through the study of the fossil record, we identified significant changes to the coccolithophore community during the warmest substages of MIS5, i.e. MIS5e. Site U1501 recorded a significant peak in coccolithophore absolute abundance related to increased productivity during MIS5e, and consequently, the highest coccolith-derived carbonate contribution to bulk calcium carbonate of the last 300 kyr. Data from cultures indicated the resilience of H. carteri towards high CO2 through the maintenance of well-preserved coccoliths. However, the growth rate, despite being constant, was slightly lower than the control culture, indicating a decreased contribution to calcite production/export under high CO2 levels. The results suggest coccolithophores may play an important, but shifting role in carbon sequestration in a warmer world. Further, this comparison contributes to improving our understanding of the potential effects of anthropogenic climate change on oceanic primary producers like coccolithophores.

Living and Fossil Coccolithophores: a tool to understand past and future climate changes

In the geological record, calcareous nannofossils are intensively studied, because they are important palaeoecological tracers. Today, as in the past, coccolithophores are really sensitive to environmental changes. So, their growth and calcification rates could be influenced by different factors such as temperature, carbonate chemistry and/or nutrient content (i.e, Erba et al., 2010; Wulff et al., 2020). The variations in nannoplankton abundance, shape and/or coccolith size could give information of past ocean-atmosphere conditions including the amount of CO2 exchange between the ocean and the atmosphere. For this research the time interval selected is the Early Aptian to Late Albian (ca. 121-100 Ma) which was characterized by important climatic and paleoenvironmental changes including a cooling event in the early late Aptian, and two “Ocean Anoxic Events”, namely the OAE 1a and OAE 1b. Particularly, the focus is on the Aptian/Albian boundary and the Oceanic Anoxic Event 1b. The whole study interval was selected because morphometrics analyses on Biscutum constans from the Western Tethys documented relatively small sized specimens in the early late Aptian (Bottini & Faucher, 2020), followed by average size increase after OAE 1b. Here, we conduct new morphometries on species with particular affinities in temperature or fertility such as Watznaueria barnesiae (oligotrophic species), Rhagodiscus asper (warm water species), Zeugrhabdotus erectus and Biscutum constans (mesotrophic species). The aim of the study is to a) see if there are any dimensional variations in different species other than B. constans; b) investigate if the species responded to paleotemperature and paleofertility changes with size variations and c) detect if the coccolith size justifies a decrease in nannoplankton calcification and how this possibly influenced the total carbon budget. Thus, in order to reach these objectives, we studied samples from ODP Site 1049 (Proto-North Atlantic) and the Piobbico core (Umbria-Marche Basin, central Italian Apennines) and we have correlated new morphometrics data with the nannofossil abundance, temperature and fertility index.

How coccolith size changed in response to paleoenvironmental variations during the Early Aptian to Late Albian?

The study of the climate changes of the last centuries allows comparison of data from historical documents, instrumental and paleodata records with multi-decadal variability arising from external forcing and internal climate variability. In this framework, the marine fossil records represent a fantastic archive to document the climatic variability over the last 500 yrs. In this framework, Globorotalia truncatulinoides oscillations have been recorded from several marine sediment cores collected in the central and western Mediterranean Sea. G. truncatulinoides represents a deep dwelling winter species in the Mediterranean Sea and its life-cycle is characterized by a vertical migration in the water column. The abundances of this species over the last 500 yrs demonstrates its potential value as bio-indicator of particular oceanographic condition during the Maunder Minimum (MM) event of the Little Ice Age (LIA). The comparison between the G. truncatulinoides abundance patterns of the Balearic Basin, central and south Tyrrhenian Sea and central and eastern Sicily Channel allows to highlight a similar response of this species during the MM event in the central-western Mediterranean Sea. The ecological meanings of this species and its peculiar high abundance percentage values in the total assemblages suggest the development of enhanced vertical mixing conditions during MM winter season with a strong advection of nutrients from the nutrient-rich deeper layers and enhances the productivity levels in the mixed layer. The intensified vertical mixing could be linked to persistence of an atmospheric blocking event recorded by several authors during the MM. In fact, this time-interval is characterized by an atmospheric blocking event. These particular climatic conditions could be responsible of intense deep vertical mixing phenomenon during the winter season producing the ideal ecological conditions for G. truncatulinoides proliferation. In addition, we suggest that maximum abundance of G. truncatulinoides left coiled is a response to more active dense water formation within the Mediterranean Sea during a cold time-period such as the MM. This research has been financially supported by the ERC-Consolidator TIMED project (REP-683237).

The planktonic foraminifera Globorotalia truncatulinoides in Central - Western Mediterranean Sea during the Little Ice Age

During the late Quaternary, the Kurdistan Region of Iraq (north-eastern part of ancient Mesopotamia) was the scenario of several fundamental cultural events including the dispersal of Homo to Eurasia, the origin of agriculture and adoption of domesticates, the beginning of urbanization, and the formation of the first state entities. The role played by climate and environmental changes on these cultural processes was highly debated, but local, continuous, and well-dated paleoclimatic records are still missing. In this contribution, we present the preliminary results of a palaeoclimatological and paleoenvironmental investigation in this area, which aims to reconstruct a detailed framework of the relationship between global climatic changes, regional environmental and hydrological responses, and human adaptation during the Late Quaternary, with a special look to the Holocene. Speleothems were collected along the eastern slopes of northern Zagros from the Hassārok Cave, near Shaqlawa township, in the northern Kurdistan Region of Iraq. Preliminary geochemical and geochronological results provide information on Holocene climatic variability in the region. Environmental and paleoclimatic data have been compared with archaeological information to infer and quantify the effects of climatic changes (if any) on human exploitation of natural resources, settlement dynamic and major shift in subsistence strategies and land use.

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Environmental and Oceanographic Conditions at the Continental Margin of the Central Basin, Northwestern Ross Sea (Antarctica) since Last Glacial Maximum

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From the Early Pleistocene to the Recent: how is Xenophora crispa biomineralization varied?