Characteristics of Grainsize and Sedimentation of Shell Bar Section in Salt Lake Qarhan, Qaidam Basin

Key words: 
• Qaidam Basin /
• shell bar section /
• grainsize /
• sedimentation environments

Abstract: Based on the grain size analysis, carbonate, magnetic susceptibility measurements on the shell bar section at Qarhan Lake in Qaidam Basin, the translation and sedimentation processes of the materials have been discussed and the lake level change history is reconstructed. The results suggest that from 38.2 to 35.5 ka C14 BP be the period of lake formation, the grain size recorded a quick lake level rise event at 35.5ka BP; from 35.533.3ka BP the grainsize indicates that the lake level was low; from 33.3 to 27.1 ka BP, the fine grainsize, higher carbonate content and low magnetic susceptibility demonstrate a high lake level period. During this time, there are three times (28.327.1 ka BP,30.329.7 ka BP and 32.132.3 ka BP) during them lake level decreased. The lake level reached it maximum between 29.7 and 28.3ka BP with a finest grainsize. Between 27.1 and 18.1ka BP, the lake level started to decrease, and from 18.1ka BP, the lake retreated abruptly with a very strong increase of the evaporation, resulted in the salt formation. After that the lake shrank further and never reached this level again.