Sedimentary Features of Salt Lakes in Xinjiang

Key words: 
• Sedimentary of salt lakes /
• Cycles /
• Speed /
• Salime minerals

Abstract: Xinjiang is the largest arid emiarid saltforming region in China,its natural environment has a geographic character of "two basins surrounded by three mountains". Many fresh lake and salt lakes are distributed in this region. It is one of the four large salt lake distribution re-gions in China. There are snore than 100 salt lakes in the region with a area of about 10,655.99 Km₂. According to the geological structure condition and natural geographic environment,five salt lake zones can be divided,l. e. Allay innermountain basin,Jungar Basin,Tianshan innermountain basins,Tarim Basin and Kunlun -Artun innermountain basins. There are Whale Lake with the altitude of 5000 m a. s. 1., and aydingkol Lake whose altitude is 155 m below the sea level and the famous salt lake playa一Lop Nur.The formation and evolution of salt lakes in Xinjiang have undwergone two stages non salt 一forming stage and salt一forming stage. There are three sedimentary types in the lacustrine deposits一elastic sediments,clay sediments and evaporate sediments. The elastic sediments represent the lacustrine sediments in the early non salt一forming stage of the salt lake forma-tion. Evaporate sediments is the lacustrine sediment in salt forming stage of salt lake forma-tion. In the evaporate sediments,there are about 38 kinds of salt minerals including carbon-ates, sulphates ,borates,chlorides such as potash and magnesium salts and nitrates .The ni-traces salt deposits is the characteristic salt deposits in salt lakes in Xinjiang.The salt一{arming stags。{salt lakes in Xinjiang began in late pleistocene一middle Holocene,¹⁴C 25 X 10⁴-5,000 a B. P.,it can be taken as the f first salt一forming stags,salt deposits can only been found in Tarpon Pasin and Lop Nur, The second salt一forming stage starts f ram middle Holocene to prcscnt with the vast salt deposits formcd in the region.The depth of the salt deposits varies from 10 to 30 m;the scdiementary sediernentary speed in-creased f ram cast to west,from north to south, The sedimentary dif f erentiatian of potash magnesium salt and nitrate salt is not obvious, sedimentary sequence is very clear, and is charactcrised by simple and multi sedimentation sequences.