A remarkable last glacial loess sedimentation at Roxolany in the Dniester Liman (Southern Ukraine)

Abstract

The study focuses on the loess–palaeosol sequence at Roxolany, exposed in the cliffs on the left bank of the Dniester Liman in the Black Sea Lowland. The sequence is one of the longest and most complete terrestrial records of Quaternary climate change in Ukraine. The Pleistocene sequence, i.e. loess, soil and fluvial units, is quite thick, i.e. about 60 m, including 30 m of L1 (Weichselian) loess: the greatest thickness in the entire Black Sea Lowland region. The paper presents the characteristics of the unique aeolian sedimentation environment in the Lower Dniester region during the last glacial cycle; our observations indicate exceptionally intense local deposition in the Last Pleniglacial. A number of luminescence dating results were obtained in several laboratories, based on various fractions and methods. The dating results for L1 loess turned out to contradict the stratigraphy of the section determined with geological methods. They were similar to each other and were clearly older than expected. Hence, to confirm the age of the deposits, various underlying factors were analysed. Our findings indicate that a combination of several circumstances could be directly or indirectly responsible for the local intensification of aeolian and depositional processes at Roxolany: (1) regional atmospheric circulation vs. orientation of relief; (2) the location and environment where the aeolian source material formed, as well as the great abundance of the deflation zone; (3) the emergence of considerable tracts of sea shelf as a result of the recession of the Black Sea, which had the effect of lowering the base level of erosion, but also of (4) revealing significant positive forms in the relief of the shelf, which undoubtedly modified anemometric conditions. The uniquely thick fossil soils within the L1 loess in the Roxolany sections may have had their origin in a continuous supply of dust during pedogenic periods.