Comparison Of Core Sediment Proxies At Different Locations Of Toson Lake In Qaidam Basin And Its Environmental Significance

The consistency of proxies at different locations in a lake is of great importance to the reliability of regional climate reconstruction.At present,a single core in the central/deep lake was usually used to reconstruct the regional climate and environment change without verification.Here we compare the same proxy among the different core sediments from different locations of Toson Lake?37°04?³7°13?N,96°50?⁹7°03?E,2808 m a.s.l?,which is located in Delingha,NE Tibetan Plateau.Core TSL15S1,TSL15S3,TSL15S7 and TSLG17 were recovered at the water depth of 1 m,16.5 m,16.5 m,and 25 m in Toson Lake,respectively.Based on the dating of ²¹⁰Pb and ¹³⁷Cs,the changes of grain size,carbonate content and other proxies were compared and analyzed,and the climate and environment changes in recent 350 years in Toson Lake were also reconstructed.In addition,we compared the lake record with Hurleg Lake and Gahai and other regional proxies.The conclusion is as follows:?1?The variations of grain size are consistent at similar locations,while they are quite different at distant locations within the lake.The grain size of sediments in the shallow water vary greatly in a short time scale,while the sedimentary environment in deep water is relatively stable.Sediment particle size composition content changes reflected the lakes hydrodynamic conditions,shallow water is influenced by many factors and the hydrodynamic condition is complex,while the deep water area with a stable sedimentary environment and sediment particle size index can reflect the change of regional climate environment,for example,in the less rainfall years,the lake water level is low and the silt component content increased;On the contrary,the silt component content in the sediment decreases.?2?The significance of sediment indexes in Tonson Lake.The variations of carbonate content can reflect the humidity of the region,effectively;the organic matter content can reflect the lake productivity;and the value of C/N instruct that aquatic organisms are the main source of organic matter in the lake.The variations of organic matter and carbonate content are consistent with each other,which indicates that carbonate may be affected by lake productivity.?3?The carbonate content of TSLG17 in Tonson Lake is the same as the grain size composition of 4⁶3?m before 1970 A.D.,but they are reversed after 1970 A.D..Compared with the measured data and other regional records,it can be concluded that it may be affected by human activities.?4?The indicators of Toson Lake,Hurleg Lake and Gahai Lake are all indicate that the regional climate tends to be arid in Qaidam Basin from Late glacial to 1960 A.D.,and then the effective humidity increased.The consistency of different lake proxy indexes shows that the sediment core proxies in the deep water area of Toson Lake can indicate regional climate change.