Sequence Stratigraphy of the Paleozoic in West Tarim Basin
- Received Date: 1999-03-09
- Rev Recd Date: 1999-06-18
- Publish Date: 1999-12-10
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Key words:
- sequence stratig raphy /
- uncomformity /
- Paleozoic /
- West Tarim
Abstract: As a result of tectonic activites,sea level changes and sediment supply rate etc., West Tarim has formed many depositional hiatuses with different forms and orders during its Paleozoic geological evolution,and its product uncomformites becomes the key element to establish the sequence stratigraphic framework in the study area.It is believed that the Paleozoic has undergone such a depositional cycles as transgrssion( O)→retrogression(S D)→transgression(C)→retrogression(P),which formed a variety of sequences with different features. The research shows that I order unconformities (sequence boundary) involve the Presinian top boundary, Ordovician top boundary and Paleozoic top bundary. According to the data of section,well and seism,as well as the characterisics and orders of different boundaries or uncomformities, two Ⅰ order sequences,six Ⅱ order sequences and twelve Ⅲ order sequences have been recognizaed for the first time.Ⅰ order sequence is formed under different tectonic settings and depositonal conditions,and Ⅱ order sequence are generally composed of four kinds of basic superimposing forms,i.e.,regression,progradation,aggradation and onlap.Ⅲ order sequence consists usually of system tracts limited by sequence boundary,transgression surface and MFS,in which TST and HST are frequently present, SMST and LST occasionally observed.In the study area,the transgressire system tracts(TST)are formed as the sea water become deeper step by step.As the sediments deposit towards the basin and,at the same time,the coast line retreats gradually,it is a sedimentary background that the highstand system tracts(HST)are formed.Different system tracts and sedimentary facies have controlled the distribution of source,reservoire and cap rocks.TST has a close relationship to the formation of source rock and reservoir and HST is generally related to the cap rock as well as reservoirs.
Citation: | CHEN Guo jun, SHI Jian, XUE Lian hua, WANG Qi, XIAO Li xin. Sequence Stratigraphy of the Paleozoic in West Tarim Basin[J]. Acta Sedimentologica Sinica, 1999, 17(4): 560-565. |