University of Southampton OCS (beta), AASP Southampton 2011

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Fluctuations in Caspian Sea Level during the Quaternary: New Evidence from Palynology, Ostracods and Climate Modelling
Keith Richards, Suzanne Leroy, Klaus Arpe, Fabienne Marret, Robert Hoogendoorn, Salomon Kroonenberg, John Athersuch

Last modified: 2011-08-16


Caspian sea level (CSL) is currently c.27m below global sea level and has undergone dramatic changes in the recent geological past. This poster shows preliminary results from an ongoing study to document the extent of CSL change in the Quaternary, and understand the mechanisms which control those changes. New palynological and micropalaeontological (mainly ostracod) data are presented from the Holocene and Pleistocene, including data from wells and shallow boreholes in the BP / AIOC operated ACG (Azeri-Chirag-Gunashli) and Shah Deniz oil and gas concessions in the central / south Caspian region, offshore Azerbaijan. The studied sections provide a more or less continuous sedimentary record for the last 2.5 million years, constrained by radiocarbon and OSL (Optically Stimulated Luminescence) ages. The link with glacial / interglacial periods and Marine (Oxygen) Isotope Stages (MIS) is inferred. The Pleistocene in this region can be sub-divided into several local stages: Khvalynian (Late Pleistocene), Khazarian (Late to Middle Pleistocene), Bakunian (Middle to Early Pleistocene), Apsheronian and Akchagylian (both Early Pleistocene) and further divided into regionally correlatable Soil Units, each of which has a distinct microfaunal (ostracod) and palynological assemblage. Variations in CSL and salinity are highlighted by ostracods and organic-walled dinoflagellate (dinocyst) assemblages, with brackish tolerant forms such as Spiniferites cruciformis, Impagidinium caspienense and Caspidinium rugosum present. Samples with fewer brackish dinocysts and ostracods often have more frequent Pediastrum (freshwater algae), interpreted as highstand events when Caspian waters were more dilute. Pollen and spore abundance and diversity in most Holocene and Pleistocene samples are high, with herbaceous taxa such as Artemisia, Chenopodiaceae, Poaceae (grass) and Sphagnum locally common. Tree pollen is dominated by Pinus, with other cold-climate forms such as Betula, Alnus, Juniperus and Salix suggesting a boreal “Taiga” forest affinity. Warm temperate tree pollen types such as Carpinus, Ulmus, Quercus and Taxodiaceae (swamp cypress) are mostly, if not entirely, reworked. This is supported by the presence of Paleogene to Late Cretaceous restricted pollen (e.g. Wodehousia) reworked from northern polar regions. New and recently published sea level curves for the Holocene and Pleistocene are presented, as are climate simulation models comparing the present day with the Last Glacial Maximum (LGM). There is a broad (but not universal) correlation between glacial periods and CSL highstands, and between interglacials and CSL lowstands. Work is ongoing to integrate the geological, biostratigraphic and climate data in order to fully understand CSL change in the recent geological past, and perhaps help predict future sea level trends in the Caspian Sea.  


Caspian Sea, palynology, ostracods, dinoflagellate cysts, pollen, sea level change, clmate modelling