1,721,074 research outputs found
Evidences of carbonate preservation on the outer continental slope in the Western Ross Sea (Hallett Ridge and Central Basin, Antarctica)
No full textLate Quaternary Antarctic Ice Sheet (AIS) changes can be investigated by analyzing marine sediments (gravity and box cores) collected on the continental shelves and along the continental margins of Antarctica. These sites are strongly influenced by the ice sheet/shelf sediment drainage and inflow/outflow of polar water masses. In this respect, the continental slope of the Western Ross Sea (WRS) is still poorly studied, in particular its history is affected by uncertainties due to the scarcity of well-preserved calcareous foraminifera preventing the production of reliable age models.
We present the results of a study made on one gravity core (KI13-C2; Melis et al., 2021) and three box-cores (KI13-bc2, bc3 and bc4; Torricella et al., 2021) located on the Hallett Ridge and in the Central Basin where the presence of carbonate-rich intervals offers the opportunity, to time-reconstruct the AIS evolving changes since the Marine Isotopic Stage (MIS) 2. These intervals correlated with other carbonate layers identified in cores collected along the WRS continental slope provide important insights about a large-scale break-up of the ice shelf/sea ice system.
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; period 2019-2021), funded by the Italian Ministry of Foreign Affairs and International Cooperation and the National Research Foundation of Korea, and thanks to a grant approved by the Department of Mathematics and Geoscience, University of Trieste.
Bibliographic references
Melis R., Capotondi L., Torricella F., Ferretti P., Geniram A., Hong J.K., Kuhn G., Khim B.-K., Kim S., Malinverno E., Yoo K.C. and Colizza E. (2021) - Last Glacial Maximum to Holocene: paleoceanography of the northwestern Ross Sea inferred from sediment core geochemistry and micropaleontology at Hallett Ridge. J. of Micropal., 40, 15-35.
Torricella F., Melis R., Malinverno E., Fontolan G., Bussi M., Capotondi L., Del Carlo P., Di Roberto A., Geniram A., Kuhn G., Khim B.-K., Morigi C., Scateni B. and Colizza E. (2021) – Environmental and Oceanographic Conditions at the Continental Margin of the Central Basin, Northwestern Ross Sea (Antarctica) Since the Last Glacial Maximum. Geosciences, 11, 155
Calcareous nannofossils, planktonic foraminifera and oxygen isotopes in the late Quaternary sapropels of the Ionian Sea
No full textForaminiferal ecozones, a high resolution proxy for the Late Quaternary biochronology in the central Mediterranean Sea
No full textThe planktic foraminiferal distribution identified in 60 cores collected in different basins of the Mediterranean Sea allowed to establish an ecostratigraphical scheme which provides a very important tool for the biochronological subdivision of the uppermost Quaterary. We identified a succession of ten ecozones during the last 23 ka in the Tyrrhenian basin and eight ecozones in the Adriatic Sea during the last 15 ka. The ecozones boundaries have been calibrated by C-14 AMS radiometric data and by the stable oxygen isotope record. The chronological framework defined by the successive bioevents shows a very high resolution (millenary scale) and evidences that the changes in the planktic microfauna occurred more or less synchronously throughout the central Mediterranean Sea. Differences due to different oceanographic settings of the basins do not affect the general distributional pattern of planktic foraminifera
Living and dead benthic foraminiferal distribution in two areas of the Ross Sea (Antarctica)
No full textWe investigated the living (stained) and dead benthic foraminiferal assemblages collected in surface sediment samples (0–1 cm) from two different areas (JOIDES Basin and Mawson Bank) of the Ross Sea (Antarctica). Samples were collected during the BEDROSE oceanographic cruise from January to February 2017. Four living and dead benthic foraminiferal fauna assemblages have been distinguished based on cluster analysis. The differences observed in the living and dead foraminiferal content from the two investigated areas are the result of taphonomic processes induced by the different oceanographic settings and environmental conditions. In the JOIDES Basin, agglutinated taxa Rhabdamminella cylindrica, Lagenammina difflugiformis, Adercotryma glomeratum, Recurvoides contortus, Reophax subfusiformis with high percentages of Trochammina group and Reophax spiculifer associated with the calcareous species Nonionella bradii and Astrononion echolsi characterize the living assemblages. The comparison between living and dead benthic foraminifera reveals considerable similarities in terms of the presence/absence of agglutinated species and differences in relative abundance of calcareous taxa. However, the major influencing factor in foraminiferal preservation appears to be the carbonate dissolution. Results from Mawson Bank show an almost exclusive presence of calcareous taxa with high percentages of Globocassidulina group in both living and dead assemblages. The dead fauna assemblage differs from the corresponding living assemblage by being more diverse documenting high-energy current influence on marine sedimentation. Graphic abstract[Figure not available: see fulltext.]
Pliocene paleoceanographic and paleoenviromental records of Stirone River through foraminiferal and palynological assemblages, and stable isotope analysis.
No full textIl record paleobiologico dei livelli anossici pleistocenici della sezione Samoggia (Appennino settentrionale)
No full text[The palaeobiological record of Pleistocene anoxic levels in the Samoggia section (northern Apennines)]. The integrated study of planktic and benthic assemblages of foraminifera from the Samoggia River section (northern Apennines, Italy), allows reconstruction of paleoenvironmental scenarios during the early Pleistocene. Up to 24 sapropels have been recognized in the section. The faunal succession suggests a basin with low salinity in the upper part of the water column and low oxygen content at the sea-bottom. High-resolution micropaleontological investigations allow identification of two intervals characterized by different paleoclimatic and paleoenvironmental conditions: the lower one starting from the Plio-Pleistocene boundary to 1.5 Ma, and the upper one from 1.5 Ma to 1.31 Ma
EX-AQUA PROJECT: PALAEOHYDROLOGICAL EXTREME EVENTS
No full textFloods and droughts are some of the most serious natural hazards for human societies. In the last decade, the catastrophic effects of these events have attracted the global attention to warrant the assessment of their magnitude and frequency, also in relation with climate change. The quantification of the recurrence time and the magnitude of the catastrophic events is mainly based on direct measures, but these are generally limited to last decades, while palaeohydrological researches can extend the records to centuries and millennia. The evidence of past flood episodes and the timing and magnitude of extreme events can be compared with modern data and provide a significant improvement on flood risk assessment. Moreover, the spatial and temporal distribution of extremes and flooding episodes can help to understand the role of climatic forcing on the occurrence of large events and the overall changes in flooding regimes during late Quaternary. In a stratigraphic and geochronological perspective, the traces of extreme palaeohydrological events can be sometimes followed from alluvial, to deltaic and marine environments, supporting or helping correlations.
In the last 20 years research methods and gathering of data related to events or phases of palaeofloods and droughts strongly improved. Some of these phases have been clearly recognized at a Mediterranean scale during Holocene, but differences can be highlighted in sub-regions (Benito et al., 2015). Thus, a standardized methodology for creating and comparing local, regional and continental databases is important.
The EX-AQUA “Palaeohydrological extreme events, evidences and archives” is a project sponsored in 2016 by TERPRO commission of INQUA and it aims at gathering data about Quaternary hydrological events, mainly considering the Holocene and with a special focus on the late-Holocene (i.e. about last 5000 years) as this includes historic times for many regions. In a global perspective, this period allow to apply a multidisciplinary approach that takes into account sedimentological, geomorphologic, biological, archaeological and documentary data (e.g. historical and written sources, chronicles). These different sources of information allow to produce high-resolution records of extreme events, which could be used as a standard dataset for comparison with other environmental records.
The scientific community involved in EX-AQUA aims at sharing information about palaeohydrological series and the methodology for their investigation in the different continents. For these and other related purposes, the meeting “EX-AQUA 2016: Palaeohydrological extreme events, evidences and archives” will be held in Padova next September, 26-28th. The conference will be followed by a 3-days fieldtrip aimed at discussing methodology and results applied in selected case studies dealing with extreme events in the Venetian-Friulian Plain, the southern Alps, the Classical Karst and Istria Peninsula
INCISED VALLEYS OF THE NORTHERN ADRIATIC SHELF: A MORPHOSTRATIGRAPHIC MARKER FOR THE LAST TRANSGRESSION
No full textIn a global perspective, fluvial incisions generally form on the continental shelfs during marine lowstand and they can be filled and partly eroded along the subsequent transgression by fluvial and estuarine deposition, as well as by sediment reworking (e.g. Maselli and Trincardi, 2013). A peculiar setting characterizes the Northern Adriatic shelf, that has a very low gradient and, apparently, it was not prone to significant incision during the LGM lowstand. On the contrary, stratigraphic and chronological data highlight the occurrence of fluvial erosive processes in the first part of the transgression.
After the LGM, the Northern Adriatic shelf, experienced a rapid submersion with dramatic environmental changes. The current morphology of the seabed above -45 m msl is the result of the strong shaping activity induced by the widespread erosive processes related to waves and currents activity after the transgressive submersion, whilst sedimentation occurred in very limited portions (Moscon et al., in press). This peculiar evolution heavily restricts the available sites that can supply information for reconstructing times and modes of the transgression. Together with the relicts of the coastal barrier systems, formed during pauses along the marine transgression, the fillings of these incised valleys are the only deposits preserved in the northern shelf between the end of LGM and the phase of maximum flooding.
The investigations carried out for the geological mapping of the sea floor recognized several completely filled incised valleys (Trincardi et al., 2011). The oceanographic cruises RISA2009, NAD2012 and ASCI2014 were partly devoted to the collection of high-resolution data (CHIRP seismo-acoustic profiles, multibeam bathymetries and stratigraphic cores) aiming at characterizing these sedimentary features.
In order to seize all the possible information out of these features a geodatabase is under construction: this database will collect all the information available for the incised valleys recognizable in the northern Adriatic area, between the Po Delta and the Slovenian-Croatian border, including VHR seismic data, shallow cores and radiocarbon dating. The preliminary work evidences several channel-like morphologies, few of them characterized by draped fillings, depth ranging from few to 20 meters, maximum widths of few hundred meters and a longitudinal development that can reach 10 kilometres. These paleo drainage systems can be generally associated to fluvial processes, but some of them underwent a shift to estuarine environments and, in some cases, lagoon tidal inlets. The analysis of their morpho-stratigraphy, along with radiocarbon dating, should offer new insights into the evolution of the area during the post-LGM transgression, providing constrains on the relative dating of these structures. Given the lack of the geological record, this approach may be of particular relevance in order to link the continental and the marine domains and to investigate the low order climatic fluctuation that strongly influenced the evolution of Lateglacial rivers
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