%0 Journal Article
%T DISCUSSION ON THE FORMATION AGE OF ARID ENVIRONMENT IN WEST CHINA<br>中国西北干旱环境的形成时代与成因探讨*
%A Li Xiaoze
%A Dong Guangrong
%A <br>李孝泽
%A 董光荣
%J 第四纪研究
%D 2006
%I 
%X When did the arid environment in West China begin has been a long debating question.Many researchers thought that it should be from the Neogene,and some insisted in much earlier origination such as the Paleogene or the Cretaceous.The actual answer should be come from geological sedimentary records.Arid environment can be identified by evidence from aeolian deposits,weathering deposits,aqueous deposits and paleontological records based on the comparison with geomorphology and sedimentology in modern arid environment.Based on the analysis of Mesozoic and Cenozoic arid sediment sequences from basins including Tarim,Dzungaria,Tsaidam,Hexi corridor and Ordos,it is concluded that arid sediments have existed continuously in these big basins since the Later Jurassic(about 160Ma),and the formation age of arid environment in West China should thus be considered as Later Jurassic.Concretely,it started at a time corresponding to the starting of the Qigu Formation((J_(3)q)) in the Tarim Basin and the Dzungaria Basin,the Hongshuigou Formation(J_(3)h)in the Tsaidam Basin,the Chijinqiao Formation(J_(3)c) and the Kushuixia Formation(J_(3)k)in the Hexi Corridor Basin,and the Fenfanghe Formation(J_(3)f) in the Ordos Basin.Although Cretaceous strata is absent in many places in the basins of Ordos,Hexi Corridor,and Dzungaria,it exists extensively in the Tarim Basin.The sediment sequence from Jurassic to Quaternary is thus complete,supplying a good basis for this study.Arid environment in West China has experienced 3 obvious evolutionary periods : (1) during Late Jurassic to Paleogene,inland reddish sediments standing for arid environment were deposited in subtropical zone;(2) in Late Tertiary,a transition from reddish deposits in subtropical zone to grayish or yellowish deposits in temperate zone was existed;(3) in Quaternary,gray or yellow arid deposits of temperate zone was dominated.The starting of arid environment at Late Jurassic in West China coincides with the warm-up event during the period from Jurassic to Middle Cretaceous,which drove the boundary of the subtropical zone to north in the Northern Hemisphere within which West China was included.By comparison with the cases in the geologic history,it can be concluded that arid environment of temperate zone in West China occurring in Neogene was mainly caused by tectonic movements,e.g.,the disappearing of the Tethys,the uplifts of the Qinghai-Tibetan Plateau,and the formation of mountains surrounding the study basins.While global climate became colder in Cenozoic,the north boundary of subtropical zone was withdrew southward and the vast area of Northwest China should have had humid weather of temperate zone formed by the planetic westerly which transferred much water vapour form west to east.However,tectonic movements including the formation of the Qinghai-Tibetan Plateau and a series of mountains around the study basins made climate developed in a different style,to be arid.Arid environment of West China is a
%K West China
%K arid environment
%K sediments
%K formation age
%K causes<br>中国西北
%K 干旱环境
%K 干旱沉积
%K 形成时代
%K 成因
%U http://www.alljournals.cn/get_abstract_url.aspx?pcid=E62459D214FD64A3C8082E4ED1ABABED5711027BBBDDD35B&cid=621CF755B1A341E5&jid=EA07051745CDC8D89D5F01A3A4CFE6A9&aid=046BA978D9E498C4&yid=37904DC365DD7266&vid=96C778EE049EE47D&iid=B31275AF3241DB2D&sid=2DEC3FE1EFC628C2&eid=46CB56AABC2765FF&journal_id=1001-7410&journal_name=第四纪研究&referenced_num=2&reference_num=99