Sedimentary Character of Upper Triassic Series Xujiahe Formation in Yuanba Area of Northeastern Sichuan

Some geologists thought that sediment type of upper Triassic series Xujiahe formation is lacustrine facies,not large-scale river-delta sediments in Yuanba area of northeastern Sichuan. These viewpoint may not correct according to ours recent research in the area. Founding analysing wells,rock core,outcrop,seismic data that Xujiahe formation stratigraphic character in Yuanba is similar to other areas that strata can be divided 5 rock section.Section 1,3,5 is mud-siltstone and correction mark in basin. Section 2,4 is sandstone and large-scale braided river delta plain-dalta front including braided channel-main reservoir,Key of river delta sediments formed is provenance that come from Micang mountain orogenic belt,not Longmen mountain orogenic belt.