Late Jurassic Stratigraphic Division And Sedimentary Environment In Baoji Area,Tibet

Jurassic of Tethys tectonic domain is one of the most important oil and gas generation and reservoir layer in the world.Coqen basin is located in the east of Tethys tectonic domain.Jurassic of Coqen basin and its adjacent areas contain Renduo formation,Rila formation,Jienu group and Tukari formation.But,this formations and groups researches are weak and have little attention to the evalution of oil and gas.This thesis researched 5 Jurassic stratigraphic setions and 2 Jurassic corals points.We find 35 genus 67 species Late Jurassic corals in the studied area.These corals indicate that the yielding strata is not the Paleozoic strata as it was thought previously.The yielding strata are correlated to be the Late Jurassic Tukari formation on basis of this study.Tukarizu formation provides a window to know Late Jurassic of Ban'ge-Basu stratigraphic division and Coqen basin.We divided Late Jurassic of studied area into Sabozhibule formation,Tukari formation,Duoni formation.Tukarizu is in conformity relation with Sabozhibule formation which is under it and Duoni formation which is on the top of it.In this division of Late Jurassic,carbonate layer of Renduo formation,carbonate layer of Rila formation and carbonate layer of Cuoguo formation will be divided into Tukari formation.Another,Duoni formation provide a new clue for the boundary line of Jurassic and Cretaceous.After analysising the sedimentary environment of Tukari formation,Baoji area is in carbonate platform in Late Jurassic Oxfordian-Kimmeridgian.Tukari formation,Renduo formation,Rila formation and Cuoguo formation indicate that the Upper Jurassic Oxfordian-Kimmeridgian in the Coq(?)n Basin is characteristic by the carbonate rock.The discovery of the Tukari formation increases the value of oil and gas exploration of the Coqen Basin,because it provides critical stratigraphic evidence for the existence of the Late Jurassic reef facies carbonate rock.