Paleoenvironmental changes since the late Pleistocene based on sporopollen records in the area from the Tuotuo River-Kunlun River, Qinghai-Tibet Plateau

Comparative study of the data of the late Pleistocene sporopollen in lacustrine deposits of Yaxi Co Lake in the reaches of the Tuotuo River and lacustrine deposits on banks of the Xijir Ulan Lake and fluvial deposits of the Kunhm River in the Qinghai-Tibet Plateau indicates that there is a pronounced negative correlation in percentages between the two pollen markers Artemisia and Chenopodiaceae in the area. From south to north and from older to younger strata, the species of sporopollen and number of arbores diminished gradually, the percentages of pollen of Gramineae decreased progressively and spores of fern were scarce. The dry shrubs-grassland vegetation represented by Nitraria appeared in the southern part of the study area during the early part of the late Pleistocene. Dry-wet grassland vegetation represented by Artemisia and Gramineae appeared at 30-10 ka BP in the area. In general, the southern part of the area was wetter than the northern part according to the paleoenvironment reconstructed by the late Pleistocene sporopollen analysis. This feature has great significance for the reconstruction of the paleovegetation and paleoenvironmental of the Qinghai-Tibet Plateau during the late Pleistocene.