THE PROCESSES AND ORIGIN OF LOESS SEDIMENTATION DURING THE BOLLING-ALLEROD PERIOD IN THE ILI BASIN, CENTRAL ASIA

The Ili loess, owing to its central Asian position, is an important archive for the westerlies-dominant climate and environment change. A reliable dating is critical for paleoclimate reconstruction and global correlation, however, previous research has showed dating the Ili loess remained controversial. Based on the OSL chronology, grain size analysis, and elementary data, we conclude that: (1) The loess in the Ili Basin originated from the flood plain and desert of the lower reach of the Ili River via the westerly wind. (2) The apparent increase of loess accumulation rate during the Bølling-Allerød period, a prevalent phenomenon in the Ili Basin, is attributed to the wetter and warmer climate, which provides an environment favourable of trapping eaolian sediments and increasing fluvial sediment of the Ili River. (3) The reduction of fluvial sediment of the Ili River led to the declining accumulation of the Ili loess since the Holocene.