Late Pleistocene to Holocene evolution of the Emba Delta, Kazakhstan, and coastline of the north-eastern Caspian Sea: Sediment, ostracods, pollen and dinoflagellate cyst records

Abstract

Six cores, each approximately 10m long, of late Pleistocene to Holocene age were studied from the Emba Delta region in the north-eastern Caspian Sea. Radiocarbon dates provide ages within the range of 47,820 to 12,020calBP for the middle sections, and for post-1950 close to surface. The ages fall within Marine Isotope Stage (MIS) 3, MIS 2 and MIS 1 (with MIS 4 also inferred). Four lithological units are present, each separated by an erosional contact. Unit 4 is equated with MIS 4 and consists of over-consolidated, east-west trending aeolian sands deposited during the late Pleistocene Atelian lowstand. Unit 3 is equated with MIS 3 and is a low-energy, shallow open water or lagoonal deposit based on ostracod faunas. Pollen from mesophilic trees is common, confirming warm climatic conditions. Floristic elements such as Engelhardia and Carya were shared with East Asia. Frequent Taxodiaceae pollen occurs, derived from Glyptostrobus pensilis, a seasonal freshwater swamp tree, now found naturally only in isolated relict stands in East Asia. This suggests that the north-eastern Caspian region was a ‘refugium’ supporting Glyptostrobus swamp vegetation during MIS 3. There is no evidence to indicate that these are reworked occurrences. Unit 2 consists of early Khvalynian transgressive barrier sands and Unit 1 of shoreface sands and muds of Holocene age. The late Khvalynian highstand and the Last Glacial Maximum (LGM) record are eroded by the Mangyshlak unconformity after ca. 12,500calBP. The Holocene interval contains frequent foraminifera and dinoflagellate cysts (dinocysts) of restricted ‘marine’ affinity (e.g. Lingulodinium machaerophorum). The dinocysts Pterocysta cruciformis and Impagidinium inaequalis are found commonly in the Caspian Sea for the first time. Results are compared with palynological and ostracod assemblages in surface samples from the eastern Caspian Sea coastal region.