塔里木盆地石炭系泥岩沉积时的古盐度分析  

The Palaeosalinity Analysis of Carboniferous Mudstone,Tarim Basin

作　　者：许璟[1] 蒲仁海[1] 杨林[2] 李艾红[2] 

机构地区：[1]大陆动力学国家重点实验室西北大学地质系,西安710069 [2]中国石油化工股份有限公司西北分公司研究院,乌鲁木齐830011

出　　处：《沉积学报》2010年第3期509-517,共9页Acta Sedimentologica Sinica

基　　金：中国石油化工股份有限公司海相前瞻性项目(编号:YPH08114)资助

摘　　要：通过对塔里木盆地巴楚、塔中、塔河地区井下及巴楚小海子露头、阿克苏四石厂露头的石炭系泥岩中黏土矿物、微量和常量元素的测定,利用Adam s和Couch古盐度计算公式、Walker相当硼判定法及锶钡比值法定量—半定量地分析了该区石炭系泥岩沉积时的古盐度特征,结果表明古盐度在4.7‰～33.9‰,大部分为半咸水沉积,其次为淡水—微咸水沉积,个别为咸水沉积;且古盐度变化明显,平面上巴楚组泥岩段泥岩总体具有从塔东北向塔西南古盐度变大的趋势;卡拉沙依组砂泥岩段泥岩在塔中古盐度最小,塔西南最大,塔北居中。由于沉积物中泥岩沉积时的古盐度特征是沉积环境的判别标志之一,因此它对有争议的卡拉沙依组砂泥岩段及巴楚组角砾岩段沉积环境的判定提供了沉积水体性质方面的依据。石炭系泥岩沉积时的古盐度与该时期海平面升降及沉积相演化有关,该泥岩形成于石炭纪海平面相对下降或上升缓慢、古盐度相对较低的沉积环境。Though the analysis of clay minerals,major and trace elements of the Carboniferous mudstone samples collected from cores in Bachu,Tazhong and Tahe areas and field outcrops around Xiaohaizi in Bachu and Sishichang in Akesu,palaeosalinity character of water environment when this mudstone was deposited in these regions was revealed by quantitative semiquantitative analysis involving calculation using Adams and Couch palaeosalinity formula,equivalent boron determinate method suggested by Walker and strontium-barium ratio method.The results indicate the range of palaeosalnity is 4.7‰～33.9‰,and display that the majority of mudstone samples show semi-saltwater sedimentary environment and freshwater-brackish environment is secondary while saltwater environment is less.In plane view,from northeast of the basin to southwest,the palaeosalinity concentration of mudstone in Mudstone Section,Bachu Formation increased in a general view.Mudstone in Sandstone and Mudstone Section,Kalashayi Formation shows the minimal palaeosalinity concentration in the center and the maximal in the southwest part of the basin,and in the north part of the basin,the palaeosalinity concentration is moderate.Owing to palaeosalinity information extracted form mudstone is one of the indications to determine the sedimentary environment,it can provide important reference in aspect of water character for identifying controversial sedimentary environment of Sandstone and Mudstone Section in Kalashayi Formation and Breccia Section in Bachu Formation.Palaeosalinity of water environment when Carboniferous mudstone was deposited has a good correlation with eustacy and sedimentary facies evolution in this period,and these mudstone was formed in sedimentary environment in which sea level is relatively in fall or slow rise and palaeosalinity is relatively low.

关 键 词：古盐度 泥岩 沉积环境 海平面变化 石炭系 塔里木盆地 

分 类 号：P534.45[天文地球—古生物学与地层学] P588.22[天文地球—地质学]