西藏南部江孜盆地的演化特征
- 1. 成都地质矿产研究所 成都 610082;
- 2. 成都理工学院 成都 610059
基金项目:
西藏科委重点项目(990107);国土资源部定向基金项目(97042)联合资助
作者简介:
彭勇民,男,1965年出生,副研究员,沉积学与盆地分析
- 收稿日期:
2000-09-26
- 修回日期:
2001-02-13
- 刊出日期:
2001-09-10
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。各个阶段具有不同的演化特点。
Development of Jomzi Basin in Southern Tibet
- 1. Chengdu Institute of Geology and Mineral Resources,Chengdu 610082;
- 2. Chengdu University of Technology,Chengdu 610059
- Received Date:
2000-09-26
- Rev Recd Date:
2001-02-13
- Publish Date:
2001-09-10
Abstract: The gravity flow depositions were formed by the debris,sliding and turbidity flows in Late Jurassic-Early Cre-taceous in Shalagang ore afea 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,induding two type-1 and six type-2 sequences.The framework 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 about40 Ma and the estimated average time of every three-order sequence was 5 Ma.Sequence l(SQl)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 calcios-slide bodies and minor turbidty 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 stragraphy,depesitional development of slope setting are divided into 4 stages: (1)Relatively steep terrigenous slope,corresonding to SQ1 and SQ2.In early time,calcious and terrigenous debris-flow sediments were accumulated in relatively steep slope toe.In late time,some parts of slope were cut by channel,and slope channel filling-sequence with debris-flow conglomerates and conglomerate-bearing sandstones was formed.(2)Reatively gentle terrigenous slope,corresponding to SQ3.with rising of sea level and deepening of water body,debris-flows lacked or slightly developed. It implied that slope was becoming gentle,but sandyslid bodied characterized slope.(3)Siliceous submarine fan,corresponding to SQ4.With continuos rising of sea level and halting of terrigenous supply,siliceous submarine fan was dominated over formal terrigenous gravety-flow sediments,and slope deepened again.(4)Terrigenous submarine fan,corresponding to S05.Similar to SQ5,SQ6,SQ7and SQ8 were also characterized by the development of terrigenous submarine fan.In the end of the forth stage,with large-size fast falling of sea-level once again,greatly-thick slope escallication which switched 500--600 Km and distributed widely along Shalagang-Jomzi-Zhongba areas and stopped the growth of submarine fan.After Late Cretaceous,Jomzi basin was gradually filled out by shallow-water sediments and disappeared.
彭勇民, 李金高, 刘家铎, 姚鹏. 西藏南部江孜盆地的演化特征[J]. 沉积学报, 2001, 19(3): 345-350.
引用本文: |
彭勇民, 李金高, 刘家铎, 姚鹏. 西藏南部江孜盆地的演化特征[J]. 沉积学报, 2001, 19(3): 345-350.
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PENG Yong min, LI Jin gao, LIU Jia duo, YAO Peng. Development of Jomzi Basin in Southern Tibet[J]. Acta Sedimentologica Sinica, 2001, 19(3): 345-350.
Citation: |
PENG Yong min, LI Jin gao, LIU Jia duo, YAO Peng. Development of Jomzi Basin in Southern Tibet[J]. Acta Sedimentologica Sinica, 2001, 19(3): 345-350.
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