Conference:
European Geosciences Union 2005, Geophysical Research Abstracts, Vol. 7, 04114.
Author:
Philippe Sorrel, Speranta-Maria Popescu, Martin Head.
Abstract:
The Aral Sea is an excellent site for studying the influence of climate, tectonics and anthropogenic impact on the development of hydrographic conditions and on landform evolution in an endorheic basin. From a core retrieved at Chernyshov Bay in the NW Large Aral Sea (Kazakhstan) we present dinoflagellate cyst analyses with a sampling resolution of 15 to 20 years. At most core levels samples are rich in cysts but species richness is low (total diversity: 16 species). The dominant morphotypes are Lingulodinium machaerophorum with large variation in process length and Impagidinium caspienense, a species recently described from the Caspian Sea. The aquatic palynomorphs Pediastrum and cysts of Radiosperma corbiferum represent freshwater inflow into the lake. The data are used to reconstruct salinity as expressed in lake level changes during the last 1900 years. We report and quantify for the first time prominent salinity variations from the northern part of the Great Aral Sea Basin. During sea-level highstands, Impagidinium caspienense, representing brackish conditions with salinities of about 10–15 psu, prevail. The assemblages with L. machaerophorum, document lake lowstands from approximately AD 100-500, AD 950-1300, possibly between AD 1500-1600, and since the 1960ties. Significant erosion of marine Palaeogene deposits, including those of Eocene age, in the hinterland was also evidenced.