Until recently, the reservoir age correction (R) values for two large brackish water lakes in Central Asia, Caspian Sea and Aral Sea, were practically unknown. Rapid environmental changes, especially in the Aral Sea region, require the study of this subject for correct interpretation of the Holocene radiocarbon dates obtained on mollusc shells. Mollusc samples for the Caspian Sea were obtained from Paleontological Institute (Russian Academy of Sciences) where the collections, originally assembled at the end of nineteenth – beginning of the twentieth centuries by N. I. Andrusov and V. D. Golubiatnikov, are deposited. For the northern part of Caspian Sea, two samples were chosen, from the Chechen' Island and the Sulak River mouth. In southern part of the sea, two samples, from the Cheleken Peninsula and Garabogaz Spit, were selected. For the northern coast, the R is estimated as ca. 420 yrs, which is consistent with single R value known previously from the Kulalai (Tyuleni) Island, ca. 380 yrs (Olsson 1980). For the southern coast, the R is ca. 390 yrs. Thus, the average R value for the Caspian Sea may be established as ca. 400 yrs. Because shell samples were collected from the modern beach assemblages, the shells reworked from the Holocene and Late Pleistocene deposits could also be collected. In our dataset, a few samples with much older age compare with the ‘pre-bomb' specimens were obtained. The Didacna crassa sample from the Cheleken Peninsula gave age of ca. 3000 BP, and Didacna trigonoides sample from the city of Baku showed age of ca. 12,200 BP. In the Aral Sea, the particular problem is that the pre-bomb samples in museum collections are very rare. We were able to obtain three Cerastoderma sp. shells collected alive at the southern and eastern shores in 1936-1944 by N. A. Alekseev (the results of study will be presented at Conference). The attempt to estimate the R value by measuring the 14C age of water plants, collected mainly by L. S. Berg in 1898-1928, was less successful. The apparent ages of Saggitaria trifolia, Butomus umbellatus, Potamogeton perfoliatus, Potamogeton lucens, and Ruppia maritima vary from ca. 100 BP to ca. 1100 BP. The delta 13C values, from -13.2 to -29.2 per mill, show that these plants absorbed atmospheric carbon dioxide, and therefore are not suitable for study of the reservoir effect.
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