【作者】 陈广义；

【导师】 伊海生；

【作者基本信息】 成都理工大学 ， 地质学， 2010， 硕士

【摘要】 柴达木盆地是青藏高原北部最大的内陆盆地,其发育既受制于西部昆仑山及青藏高原的崛起,同时也受制于北部阿尔金断裂的走滑活动。柴达木盆地西部新生代地层出露齐全,分布广,沉积厚度大。本论文以柴达木盆地西部的新生代地层为研究对象,选择该地区野外露头出露良好、沉积连续、地层出露完整并且有高精度年代地层控制的长尾台剖面以及西岔沟剖面进行测制,系统采集湖相碳酸盐岩样品,进行野外沉积特征观察以及室内薄片鉴定,分析湖相碳酸盐岩沉积序列,划分沉积相,提出柴达木盆地西部新生代湖相碳酸盐岩的沉积模式。通过岩相组合特征以及野外沉积构造分析,对柴达木盆地西部古湖盆主要识别出河流相、湖泊相、三角洲相。其中河流相以及三角洲相沉积了大套砾岩、含砾粗砂岩、细砂岩及泥岩等碎屑岩,主要集中在下干柴沟组的下部以及上油砂山组上部至狮子沟组。湖泊相沉积分布在下干柴沟组的中上部直至上油砂山组下部。根据野外观察及室内薄片鉴定,共识别出以下几种湖相碳酸盐岩类型:亮晶鲕粒灰(云)岩、泥晶砂屑灰(云)岩、藻团块灰(云)岩、生物碎屑泥晶灰(云)岩、叠层石灰岩。根据柴达木盆地西部新生代地层发育的湖相碳酸盐岩岩相组合序列,分析了碳酸盐岩的沉积环境。其中,亮晶鲕粒灰(云)岩的沉积环境为滨浅湖浅滩沉积,岩相序列底部的砾岩、含砾粗砂岩以及细砂岩为滨浅湖砂坝沉积,顶部的细砂岩、泥岩为滨浅湖泥坪沉积;泥晶砂屑灰(云)岩的沉积环境为滨浅湖泥坪,下部的灰黑色粗砂岩、灰红色砂岩、黄灰色钙质砂岩为滨浅湖砂坝沉积;藻团块灰(云)岩以及叠层石灰岩的沉积环境相同,均为滨浅湖藻坪沉积,下部的砾岩、砂岩为滨浅湖砂坝沉积,上部的细砂岩、泥岩为泥坪沉积;生物碎屑泥晶灰(云)岩的沉积环境为滨浅湖介壳滩,被泥坪相粉砂质泥岩、泥岩覆盖。综合前面的研究结论,并借鉴前人对现代以及古代湖相碳酸盐岩沉积模式的研究,提出了柴达木盆地西部新生代湖相碳酸盐岩的沉积模式。更多还原

【Abstract】 Qaidam Basin is the largest inland basin in northern Qinghai-Tibet plateau, the development of Qaidam Basin is controlled by rise of the south of the Kunlun Mountains and of the Tibetan Plateau and by activity of the western Altyn strike-slip fault. The characteristic of Qaidam Basin is Cenozoic strata outcrop integrated, widely distributed and large sedimentary thickness.This paper is studyed on Cenozoic strata of west Qaidam Basin in northern Qinghai-Tibet Plateau. Choose Changweitai and Xichagou section which has better outcrop, successive sedimentation and high-precision chronostratigraphy control to collect lacustrine carbonate rocks samples, observe sedimentary characteristics of the wild and identify thin-section, analysis depositional sequence and sedimentary facies of lacustrine carbonate rocks, finally present lacustrine carbonate rocks depositional model of Cenozoic formation of west Qaidam Basin.By lithofacies characteristics and sedimentary structures of the wild, obtain that there are fluvial facies, lacustrine and fan delta facies. Lots of roundstone, pebbled sandstone, fine sandstone, mudstone are deposit in fluvial facies and fan delta facies which are converge at the lower part of Xiaganchaigou Formation and the upper part of Shangyoushashan Formation-Shizigou Formation. lacustrine facies is distribute from the mid-upper Xiaganchaigou Formation to the lower Shangyoushashan Formation.Based on field observation and thin-section identification, several types of lacustrine carbonate rocks are identified as follows: oosparite, calcarenite, algal clast limestones, bioclastic limestones, algal stromatolitic limestones.According to lacustrine carbonate rocks lithofacies sequence of Cenozoic strata of west Qaidam Basin, depositional environment of lacustrine carbonate rocks are analysed. Oosparite depositional environment is littoral-shallow lake riffle, underlying gravel, pebbly coarse sandstone and packsand are deposit at littoral-shallow lake sandy dam, upper packsand and mudstone are mud flat; Depositional environment of calcarenite is littoral-shallow lake mud flat, gray dark coarse sandstone, gray red sandstone, yellow gray calcareous sandstone are littoral-shallow lake sandy dam; Depositional environment of algal clast limestones and algal stromatolitic limestones are similar, both are littoral-shallow lake algal flats, underlying sandstone and are deposit at littoral-shallow lake sandy dam, upper packsand and mudstone are mud flat depositions; Depositional environment of bioclastic limestones are littoral-shallow lake shell bank and covered by mud flat mudstone and pelitic siltstone.Through the above study, and learn from predecessors of modern and ancient lacustrine depositional model of carbonate rocks, lacustrine carbonate rocks sedimentary model of the Cenozoic in western Qaidam Basin is proposed.更多还原