Diatoms from the cores containing Holocene deposits from the central part of the Volga Delta (Baraniy Bugor region)

Abstract

In this article we present the study of fossil diatom assemblages in the two cores from the central part of the Volga Delta. In the core C1 from the right bank of the Bolda River diatoms were found in the dark-grey lithological layer consisting of silt. In this layer we distinguish two stages of sedimentation. The first stage corresponds to more stagnant water regime and is represented by prevailing Epithemia adnata (30,0 %) and Aulacoseira granulata (15,7%). These conditions are replaced by more riverine-like ones during the process of sedimentation. The structure of diatom assemblages of the riverine-like conditions is similar to the assemblages from the environments of shallow overgrowing distributary channels in the recent Volga Delta: A. granulata (72%), Stephanodiscus astraea var. intermedia и Aulacoseira italica (4,3 и 3,4% respectively). In the core BB9, taken from the left bank of the Bolda River, we studied the upper part of the sediments, which probably deposed in a bay (liman), and reconstruct low-flow conditions or environments of small rivers.