Sediment and Atratum Succession Characteristic of the Last Stage of Late Triassic and Middle Jurassic in Northwest Guizhou and the Nearby Area

Le résumé fourni par la source

The last stage of late Triassic and middle Jurassic in northwest Guizhou and the nearby area is a land facies sedimentary period after the sea facies sediment caused by indosinian movement.Its sedimentary characteristic is the lake sediment is predominant,and the nest is the river sediment.In the vertical dimension,it shows that the river sediment appears in the lower Er'qiao formation and upper Xiashaximiao formation and Shangshaximiao formation of the stratum succession in this period,the lake sediment crosses the stratum in the whole study period,especially develops well in the Bailiujing formation.The river sediment is dualistic structure,the lower part is flat sediment and the upper part is embankment sediment.The lake sediment is divided into three sub-fasies sediments: lakeside,low lake and deep lake,it shows two procession features from shallow to deep in the stratum succession.The stratum of the studying period has the feature of procession,the unconformable plane and relevant conformable plane as the succession plane,it can be divided into five sedimentary sequences,and each sequence is made of transgressive systems tract and regressive system tract,reflects 5 times advance and retreat translations on the lake plane.

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