A Recent Study on Sedimentary Sequence of Southeastern Badain Jaran Desert since 150 ka BP

Abstract

The geological boundaries of the-Middle-Pleistocene/the-Upper-Pleistocene, Lower the-Upper-Pleistocene/Upper the-Upper-Pleistocene and Upper the-Upper-Pleistocene /Holocene in Chagelebulu section, situated at the southeastern of the Badain Jaran Desert, take place at the deposition interfaces of 59AGS/60L, 39FD/40G and 9L/10FD respectively and their time boundaries are roughly at 150 ka BP, 75 ka BP and 10 ka BP in turn. The study shows that the section has recorded 25 cycles of alternative change processes between desert and lacustrine depositions since 150 ka BP. Comprehensive study shows, by distribution characteristics of the grain-size and SiO_(2), Al_(2)O_(3), Fe_(2)O_(3), FeO in layers in the section and palaeoecology indicated by fossil mollusks, that the sedimentary cycles were products of many times of normal and reversal alternation evolutions between desert and inter-desert periods in the non-monsoon sandy land caused by vicissitudinary winter and summer monsoons under influence of glacial and interglacial climates in the Northern Hemisphere from that time on.