Research On Sedimentary System And Sequence Stratigraphy Of The Xujiahe Formation Of The Upper Triassic Series In Western Sichuan Foreland Basin

Western Sichuan Foreland basin in front of the Longmen mountain thrust belt is one of the typical foreland basin. The Xujiahe Formation of the Upper Triassic Series is rich in resource capacity, but very low in proved rate, the potential of oil and gas exploration is huge. In addition, it exists many controversial in stratigraphy correlation and sedimentary system of the Xujiahe Formation, and so on. It is necessary to have an expanding research on the Xujiahe Formation in Western Sichuan Foreland basin.Based on sedimentology,sequence stratigraphy and lithofacies-paleogeography for theoretical guidance, the thesis researchs the stratigraphy, sedimentary system, and sequence stratigraphy of the Xujiahe Formation of the Upper Triassic in Western Sichuan Foreland basin by using geologic, logging and seismic methods. and makes the sequence-paleography maps which reveals the evolution and features of the sequence-lithofacies paleography in Western Sichuan Foreland basin Xujiahe Formation.The thesis correlates stratigraphy and establishes the schema of stratigraphic classifications of the Xujiahe Formation in Western Sichuan Foreland basin after carefully observing outcrop and rock core and comprehensively analysising plenty of regional geology stratigraphy information.On the basis of previous research, by comprehensively analysing the regional geotectonic setting and sedimentary setting data, observing outcrop and core, and then investigating logging profile, the thesis divids the sedimentary system of the Xujiahe Formation into 3 types of sedimentary system groups and 6 types of sedimentary systems. It deeply investigates the characteristics of sedimentary facies, sedimentary subfacies and sedimentary microfacies, and establishes the sedimentary models of the Xujiahe Formation in Western Sichuan Foreland basin.On the basis of analysis on seismic sequence, the thesis divides the Xujiahe Formation into 3 tectonic sequence and 6 third sequence through identifies various kinds of sequence interface and under the guidance of classics sequence stratigraphy.It establishs sequence stratigraphic framework of the Xujiahe Formation of the Upper Triassic in Western Sichuan Foreland basin,and also deeply investigates the characteristics of all levels sequence.The thesis makes sequence-lithofacies paleography maps of the Xujiahe Formation of the Upper Triassic in Western Sichuan Foreland basin by unit of third sequence, which reveals the evolution and feature of sequence-lithofacies paleography in various period.