Lacustrine Sediments Characteristics And Environment Indication Of The Da’erduo District In The Lop Nur Since 22.70Ka BP

Lacustrine sediments in the Da’erduo district in the Lop Nur are one of the major archives of past global climate and environmental change. Lacustrine sediments studies play many important roles,including reconstructing paleoclimatic change determining, identifying mechanisms driving climate change of an area, and exploring relationships between human activities and natural processes.We took typical lake sediment profiles from the center to the shore of Da’erduo lake, and analyzed in the Chronology, sedimental physical indexs and geochemical indicators, Data for several climate and environmental change indicators were used to reconstruct the climate environment change sequence in the Da’erduo lake district from 22.70 ka B.P.. This sequence provided further insight into regional climate and environment change and its response to global change.This information on geochemical sedimentary characteristics provided the basis for exploring a variety of dry salt lake formations and their change mechanisms and estalish guidelines for the reasonable exploitation and sustainable use of their resources.Major conclusions:(1) The Lithologic properties from the profiles revealed that the upper sediment is covered by a solid salt crust and that its thinkness at the shore is larger than in the center. Below the salt crust, the sediment mainly consists of sand and sandy loam, with different particle sizes of rock salt and the mineral gypsum;To some degree,lithologic changes reflect an obvious environmental evolutionary trend of increased warming and aridity since 22.70 ka BP. Comparing these results with other dating methods, we conclude that the sediment appears to contain ancient climate and environmental change information of quaternary period at the end of the last glacial period and holocene(Q4) that occurred in the Lop Nur region.(2) A variety of indirect measures of environmental and climate change were evaluated,including grainsize, ehroma, magnetic susceptibility,carbonate content, total organic carbon, gypsum content,and the geochemical elements and element(multielement composite) ratio.Based on the information from three profiles, Lake sedimentary characteristics and environment datas also supported the conclution that the environmental trend went from warm wet to warm dry in the Lop Nur area since 22.70 ka BP.(3) Multivariate statistical methods proved useful in interpreting geochemical data. Based on the results,we reconstructed the region’s climate and environment with respect to temperature and precipitation.Evolutionary process of the climate could be divided into eight stages:changing from warm-dry to cold-wet,to warm-wet,to warmer,to colder-wetter,then to cold-wet and warm-dry fluctuation,to warm-dry and to intensidied arid. The lake levels changed from deep to shallow since 22.70 ka BP.(4) This study showed that lake sediments in the Da’erduo district had a specific response to global change. The lake sediments recorded detailed information about the Wurm glacial stage, The Bowling interglacial epoch,the Younger Dryas and the Medieval Warm Period. Compared with other lakes in Xinjiang, the information recorded from Da’erduo district lake sediments had the region’s characteristics.