10) New palynological records from the Holocene and Late Pleistocene of the Volga delta

KEITH RICHARDS(1) AND NATALIYA BOLIKHOVSKAYA(2)

(1) KrA Stratigraphic, Deganwy, UK

(2) Dept of Geography, Moscow State University, Russian Federation 

Talk presented at the IPC XII, Bonn, Germany, Sept 2008

New palynological records from the Holocene and Late Pleistocene of the Volga delta (Russian Federation) and the north Caspian region, and their implications for vegetation & climate history, delta evolution and Holocene Caspian sea level change

New palynological data are presented from the Holocene and Late Pleistocene of the Volga Delta. The data are from shallow (c.10m) cores taken from the Astrakhan Biosphere Reserve, close to Damchik village. Radiocarbon dates are available from most cores. Around 200 samples were studied from 8 cores, and most contained rich recovery of palynomorphs, including pollen, spores, algae and dinocysts. The pollen flora includes frequent Gramineae, Artemisia and Chenopodiaceae, indicating a strong pollen influx from non-forest vegetation (steppe, semi-desert and desert). Pinus sylvestris is locally common and is a long-distance, mainly wind-dispersed element. Tree pollen types such as Quercus, Ulmus, Tilia and Carpinus are also locally common. The data are compared with existing pollen records from Solenoe Zajmishche, c.200km to the north, where maxima of tree pollen provide evidence for several Holocene climatic optimum periods (Bolikhovskaya 1995). Willow trees occur mainly on natural levees between the main Volga River channels at present, and the distribution of Salix pollen in the cores gives an indication of channel migration over time. Pollen from emergent reeds (e.g. Typha and Sparganium) and submerged aquatic plants (e.g. Potamogeton) indicate the relative extent of reedbeds and open water habitats. Algal bodies and dinocysts illustrate the relative importance of freshwater and brackish (Caspian) influences. Late Pleistocene to Early Holocene deposits typically consist of reddish brown clays, and are characterised palynologically by frequent fungal spores and hyphae. Channel deposits, identified on shallow seismic, contain frequent Mesozoic reworking. The first phase of Holocene delta deposition occurred after c.7000 BP and is marked by a “flood” of dinocysts (mainly Spiniferites cruciformis) overlain by an interval with increased freshwater components (e.g. Pediastrum). The second phase occurs after c.3000 BP and includes several short-lived transgressions, each marked by dinocyst “floods” (mainly Impagidinium caspienense). Pinus sylvestris pollen is also frequent and coincides with an increase in the abundance and diversity of Mesozoic reworking. Most boreholes also have increased numbers of dinocysts within the uppermost metre of sediment, likely to represent the documented increase in Caspian Sea levels in recent historical times (since c.1980). Surface samples have also been studied palynologically from around the north Caspian region, including Dagestan, the present-day Volga Delta and lagoonal / isolated saline lake regions of Kazakhstan.

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