Physical properties and their relationship to texture and consolidation effects in sediments from mud volcanoes in the Anaximander mountains (Eastern Mediterranean)

1 page, 1 figureThis research is focussed on the mud volcanoes Amsterdam, Kazan and Kula located in Anaximander Mountains. These volcanoes, characterized by the presence of sediments containing gas and gas hydrate, have been sampled, recovering four gravity cores. For those sediment located inside the mud volcanoes the physical properties are controlled by lithology and volcanic processes rather than degree of compaction. This could suggest the possible present volcanic activity. Contrasting, the core located outside the Kula mud volcano displays physical properties mostly related to consolidation effects and to the type of sediment at a detailed scale, as it occurs typically in deep sea fine grained sediments. This suggests a restricted in?uence of volcanic processes outside the crate

Holocene Centenial-scale Paleoceanographic and Paleoenvironmental Patterns in the NE Mediterranean Sea

International audienceThe Eastern Mediterranean Sea lies in a climatological transition zone, under the influence of both tropical and mid-latitude climate processes. Within this basin, the Aegean Sea has been recognized as a highly sensitive area to global/regional climate change. Sediment archives provide robust evidence for changes in its hydrological properties and biogeochemical functioning as a response to past climate variability. In order to investigate the region's paleoclimatic and paleoceanographic patterns during the Holocene, with a special emphasis on the sapropel S1 interval, we have investigated marine sediment cores along a N-S transect in the Aegean and the S. Cretan Seas. We focus on combined geochemical, micropaleontological and palynological proxies, namely organic biomarkers, organic carbon and nitrogen stable isotopes, coccolithophore and pollen assemblages, aiming at reconstructing climate-related parameters such as sea surface temperature (SST), marine productivity patterns, stratification and nutricline fluctuations, continental vegetation patterns and land-sea interactions. SST patterns depict major global/regional climate fluctuations during the last glacial and deglaciation periods, depict the warm transition to the Holocene optimum, when the formation of the S1 sapropel takes place, a distinct cool episode around 8 ka BP (coeval with the S1 interruption), a conspicuous mid-Holocene warm phase (5.4-4.3 ka BP) as well as other distinct fluctuations. Diagnostic marine lipids, δ15N, and coccolithophore assemblages allow documenting the variability of primary productivity and associated organic carbon accumulation in sediments, as well as fluctuations in water column stratification and nutricline, especially during the deposition of the S1 sapropel. Combined terrigenous proxies record warm/cool and dry/humid time intervals, allowing land-sea correlations, and document changes in the delivery of terrestrial material to the sea related to climate-driven fluctuations in freshwater discharges. The network of sediment cores studied provide a better constrain of the regional climate patterns in the northeastern Mediterranean Sea and enables assessing potential time lags and gradients

Late postglacial paleoenvironmental change in the northeastern Mediterranean region: Combined palynological and molecular biomarker evidence

International audienceThree gravity cores collected from the NE Mediterranean (NEMR) across a transect from the northern Aegean Sea (North Skyros basin) to the south Cretan margin (SCM), were investigated for pollen and terrestrial biomarkers derived from epicuticular waxes of vascular plants during the last ∼20 ky. Pollen data show diversified mixed temperate forest in the northern borderlands and enhanced Mediterranean vegetation in the southern areas, documenting an N–S climatic trend. Terrestrial plant biomarkers and their diagnostic geochemical indices exhibit latitudinal patterns which are interpreted in terms of the different delivery pathways (fluvial/runoff vs. atmospheric transport), resulting from the climate conditions during different periods. During the Late Glacial and early deglaciation periods (20–14 ka BP) relatively increased humidity (H-index) is recorded in the north Aegean Sea, while in the South drier climate was the limiting factor for vegetation development. During this interval, terrestrial n-alkanes showed increased accumulation rates, suggesting massive transport of terrestrial organic matter through runoffs and rivers, followed by weaker input after 14 ka BP. After ∼11 ka BP a major expansion of forest cover is evidenced in the NEMR, accompanied by a higher H-index because of the climatic amelioration. The forest vegetation exhibited regionally different characteristics, with cool temperate taxa being more abundant in the Aegean cores, while the SCM record is being featured by Mediterranean elements. At the onset of the Holocene and throughout the Holocene Climatic Optimum the delivery of terrestrial biomarkers increased and became more significant in the Aegean sites compared to the SCM site. Within the Holocene, the average chain length (ACL) of long chain n-alkanes exhibits lower values in the northern Aegean than in the southeastern Aegean and SCM, indicating the predominance of warmer species southwards. Finally, the H-index records a conspicuous humidity increase between 5.4 and 4.3 ka BP in the south Aegean that coincides with an increase in the terrestrial biomarker supply and the deposition of a distinct sapropel-like layer, SMH (Sapropel Mid Holocene). Similar trends in T (temperature) and H indices are slightly delayed and attenuated in the northern Aegean and are accompanied by an increase in the ACL index. A noticeable increase in the accumulation rates (ARs) of terrestrial biomarkers and the HPA index values during this period are clearly recorded in all three cores, indicative of enhanced terrigenous inputs of organic matter along with higher in-situ preservation

Vegetation patterns of the last Interglacial: the record of marine core SK-3 from western Cyclades plateau (SW Aegean Sea)

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Holocene Climatic Optimum centennial-scale paleoceanography in the NE Aegean (Mediterranean sea)

Combined micropaleontological and geochemical analyses of the high-sedimentation gravity core M-4G provided new centennial-scale paleoceanographic data for sapropel S1 deposition in the NE Aegean Sea during the Holocene Climatic Optimum. Sapropel layer S1a (10.2–8.0 ka) was deposited in dysoxic to oxic bottom waters characterized by a high abundance of benthic foraminiferal species tolerating surface sediment and/or pore water oxygen depletion (e.g., Chilostomella mediterranensis, Globobulimina affinis), and the presence of Uvigerina mediterranea, which thrives in oxic mesotrophic-eutrophic environments. Preservation of organic matter (OM) is inferred based on high organic carbon as well as loliolide and isololiolide contents, while the biomarker record and the abundances of eutrophic planktonic foraminifera document enhanced productivity. High inputs of terrigenous OM are attributed to north Aegean borderland riverine inputs. Both alkenone-based sea surface temperatures (SSTs) and δO18G. bulloides records indicate cooling at 8.2 ka (S1a) and ~7.8 ka (S1 interruption). Sapropelic layer S1b (7.7–6.4 ka) is characterized by rather oxic conditions; abundances of foraminiferal species tolerant to oxygen depletion are very low compared with the U. mediterranea rise. Strongly fluctuating SSTs demonstrate repeated cooling and associated dense water formation, with a major event at 7.4 ka followed by cold spells at 7.0, 6.8, and 6.5 ka. The prominent rise of the carbon preference index within the S1b layer indicates the delivery of less degraded terrestrial OM. The increase of algal biomarkers, labile OM-feeding foraminifera and eutrophic planktonic species pinpoints an enhanced in situ marine productivity, promoted by more efficient vertical convection due to repeated cold events. The associated contributions of labile marine OM along with fresher terrestrial OM inputs after ~7.7 ka imply sources alternative/additional to the north Aegean riverine borderland sources for the influx of organic matter in the south Limnos Basin, plausibly related to the inflow of highly productive Marmara/Black Sea waters