A review on sediment samples from a deep hypersaline anoxic basin : Tyros

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Νικητίδου, Αγγελική

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The Tyros basin is a presently deep hypersaline anoxic depression in the eastern part of the Mediterranean Sea. Its presence attributes to a combination of submarine dissolution of outcropping or subcropping evaporates (Messinian) which accumulate at the slopes of the basin and at its tectonic subsidence (pull-apart mechanism) that occurs in the western Strabos trench. Therefore, this unique environment consists of two major factors. The first one is a high density stagnant bottom-water column and the second is the preservation of the organic-rich sediments of the area due to the anoxic conditions. The core (TYRO5) that was retrieved from that basin had a total length of 285cm and comprises a complex lithostratigraphic sequence due to the strong geodynamic regime of the area. The analysis conducted on sediment samples from the core TYR05 included granulometry, mineralogy, micropaleontology, bulk geochemistry and total CHNS/organic carbon (TOC). The grain size distribution along with the planktonic foraminifera presents fluctuations which coincide with changes in the lithology of the core. The mineralogical composition of the sediments confirm the evaporate influence developed on the bottom of the basin, while both geochemistry and total CHNS/TOC verify the present anoxic conditions and the existence of organic-rich sediments. The synthesis of all the above analysis suggests that the sediment core consist mostly of sapropel to sapropelic layers and that it has a rather homogeneous character, because of its high re-sedimentation rate. Subsequently, it is indicated that the sapropel units refer to an S1 type, but further analyses are needed in order to be safely determine, such as radiocarbon dating C14 and stable isotopes of O, C.

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Anoxic basin, Brine, Sedimentology, Eastern Mediterranean

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