【作者】 李尚林；

【导师】 王训练；

【作者基本信息】 中国地质大学（北京） ， 古生物学与地层学， 2005， 博士

【摘要】 本文研究藏北羌塘盆地仓来拉一带地层特征及其地质意义,主要由下列5个部分组成:　1、将研究区自北而南划分为三个地层分区:唐古拉-昌都地层分区(华南地层大区羌北-昌都-兰坪地层区)、索县-左贡分区(滇藏地层大区羌南-保山地层区)和东恰错分区(滇藏地层大区班公湖-怒江地层区)。厘定了各分区内的地层序列与地层对比关系,为区域地质研究提供重要的基础资料。　2、在研究区发现了前奥陶系基底变质岩系酉西岩组。其变质相为高绿片岩相-角闪石岩相,原岩恢复为细碎屑岩夹中酸性、中性、中基性火山岩碎屑岩和火山熔岩。在酉西岩组中局部石墨富集,是寻找石墨矿的重要线索。　3、研究区内出露的上三叠统东达村组、“甲丕拉组”和“波里拉组”可与滇西他念他翁山和藏东昌都地区同期地层相对比。沉积相研究表明东达村组和“甲丕拉组”总体上构成一套向上变深的海侵序列。东达村组自下而上为冲积扇泥石流沉积、无障壁碎屑滨岸沉积和浅水碳酸盐台地潮坪相沉积。“甲丕拉组”为干热气候条件下的碳酸盐台地潮坪沉积、障壁砂坝沉积和滨外沉积,其中有地震事件记录。“波里拉组”中发现震积岩、海啸岩以及背景沉积组成的地震-海啸-背景沉积、地震-背景沉积、海啸-背景沉积的事件沉积序列。　4、新建查吾拉组为一套产有双壳类、腕足类和海星等化石的细碎屑岩、灰岩夹粗粒长石砂岩、膏岩角砾泥晶灰岩和白色纤维状石膏层地层。其中腕足类有Burmirhynchia-Holcothyris 组合的分子,时代应为中侏罗世巴通期。查吾拉组与下伏前奥陶系基底变质岩系呈角度不整合接触,被古近系古新统—始新统的牛堡组不整合所覆。　5、在中侏罗统布曲组共识别出10 种微相类型,主要形成于碳酸盐台地的浅缓坡、中缓坡和深缓坡三种沉积环境。垂向上可识别出四个沉积旋回,组成一个相对海平面逐渐上升的海进序列。在布曲组中首次发现黑色沥青脉,认为沥青脉的形成先后经历了液态沥脉充填-破碎-方解石胶结的过程,可能是一个具备自生、自储能力的良好的油气储层,为寻找油气田提供重要线索。更多还原

【Abstract】 The present paper deals with the strata and their geological significance in the Canglaila Area of Qiangtang Basin, North Tibet, and consists mainly of the following 5 parts: 1. The study area may be divided into three stratigraphic subprovinces. They are the Tanggula-Changdu Subprovince, belonging to Northern Qiangtang-Changdu-Simao Province of South China Realm, the Suoxian-Zuogong Subprovince included in Qiangnan-Baoshan Province of Yunnan-Tibet Realm, and the Eastern Qiaze Subprovince belonging to Bangonghu-Nujiang Province of Yunnan-Tibet Realm. The stratigraphic succession, their regional distribution and correlation of the three stratigraphic subprovinces are studied. 2. The pre-Ordovician “Youxi Lithodeme”, a metamorphic series, is discovered in the area for the first time. Its degree of metamorphism is about high greenschist-amphibolie facies. The original rock of the “Youxi Lithodeme”is considered to be fine clastic rock intercalated with intermediate-acidic, intermediate, intermediate-basic pyroclastic rock and lava. 3. The Upper Triassic Dongdacun Formation, “Jiapila Formation”and “Bolila Formation”in the area may be correlative with the deposits in Taniantawong Mountain, western Yunnan and Changdu district, eastern Tibet. The Dongdacun Formation and the “Jiapila Formation”constitute a transgeressive sequence as a whole. The Dongdacun Formation is considered to consist in ascending order of debris flow deposits in alluvial fan, barrier-free clastic littoral deposits and tidal-flat deposits in shallow-water carbonate platform. The “Jiapila Formation”seems to form under the tidal-flats in carbonate platform, barrier bar and offshore environments during a xerothermal period,and earthquake events are also recorded in the formation. Three type of sedimentary sequences: earthquake-tsunami-background, earthquake-background, and tsunami-background depositional sequences are founded in the “Bolila Formation”. 4. The newly named Chawula Formation consists of fine clastic rocks and limestones intercalated with coarse grain feldspathic sandstones, breccia mudstone and white fibrous gypsum and yields bivalves, brachiopods and starfishes. The bivalve Burmirhynchia-Holcothyris Assemblage is Batongian in age. The Chawula Formation is in angular unconformable contact with the underlying the pre-Ordovicion “Youxi Lithodeme”, and is covered by the Niubao Formation of Paleocene-Eocene of age. 5. Ten main types of corbonate microfacies are distinguished in the Middle Jurassic Buqu Formation. Four sedimentary cycles may be recognized in the formation, which constitute a transgressive sequence. The formation mainly forms in 3 sedimentary environments: inner ramp, middle ramp and deep ramp. In the Buqu Formation asphaltum veins develope well and suffer successively from 3 main processes: liquid asphaltum filling-crushing-calcite cementation. It is considered that the Buqu Formation in Gongri area is not only a better oil-gas reservoir with the capability of autogeny and autodeposit, but also a prospective area of oil exploration.更多还原