西藏南部江孜盆地的演化特征  

Development of Jomzi Basin in Southern Tibet

作　　者：彭勇民[1] 李金高[2] 刘家铎[2] 姚鹏[1] 

机构地区：[1]成都地质矿产研究所,成都610082 [2]成都理工学院,成都610059

出　　处：《沉积学报》2001年第3期345-350,共6页Acta Sedimentologica Sinica

基　　金：西藏科委重点项目 (990 1 0 7);国土资源部定向基金项目 (970 4 2 )联合资助

摘　　要：位于西藏南部江孜盆地的沙拉岗矿区发育一套晚侏罗世至早白垩世的碎屑流、滑动与浊流形成的碎屑岩夹硅质岩与灰岩的沉积。在野外识别出 8个三级层序 ,包括 2个Ⅰ类层序和 6个Ⅱ类层序 ;建立了层序地层格架。在此基础上将处于斜坡背景的沉积演化大致划分为 4个阶段 :(1)相对陡的陆源斜坡阶段 ;(2 )相对平缓的陆源斜坡阶段 ;(3)硅质海底扇发育阶段 ;(4 )陆源海底扇发育阶段。The gravity flow depositions were formed by the debris, sliding and turbidity flows in Late Jurassic Early Cretaceous in Shalagang ore area of Jomzi basin located at southern Tibet, which consisted of the slope clastic rocks and interbeds of silicalites and limestones. 8 three order sequence stratigraphies are divided, including two type 1 and six type 2 sequences. The fromework of sequence stratigraphy are established. These sequences,with clear three division structures, were characterized by the gravity flow sediments of deep water slope, developed within about 40 Ma and the estimated average time of every three order sequence was 5 Ma. Sequence 1(SQ1) of type 1 consisted of the gravity flow sediments of deep water slope. The SMST of SQ2 of type 2 was composed of the prograded and aggraded sequences of lower slope channel sandstones and conglomerates to upper slope black shales which interbeddded with sliding sandy sediments and turbidity sandstones. The TST consisted of the retrograded black shales interbedded with turbidity fine siltstones of the lower slope, the CS consisted of thin bedding lamella limestones, and the HST consisted of the progradded black shales interbedded with sandy and calcious slide bodies and minor turbidity siltstones of the upper slope. The sliding sediments characterized the SQ3 of type 2. The SQ4 of type 2 consisted of siliceous turbidities. SQ5, SQ6 and SQ7 of type 2 were composed of sediments of terrigenous submarine fan. The SQ8 of type 1 were also composed of sediments of terrigenous submarine fan, and extending and reactivating of channel of inner fan towards basin was indicator of the sequence. As a whole, the formation of sequences was closely related to sea level changes, type 1 or 2 boundaries and sequences were respectively created, corresponding to fast and slow falling. Based on study of sequence stratigraphy, depositional developments of slope setting are divided into 4 stages: (1) Relatively steep terrigenous slope, corresponding to SQ1 and SQ2. I

关 键 词：滑动沉积 海底扇 层序地层 沉积演化 江孜盆地 西藏 

分 类 号：P544.4[天文地球—构造地质学] P588.2[天文地球—地质学]