Sedimentary evolution and sequence stratigraphic model of Neogene–Quaternary terrestrial foreland basin in Southwest Tarim

Abstract

Based on the research results of stratigraphic sedimentary facies, plane maps of sedimentary facies for four periods of the Neogene terrestrial foreland basin in Southwest Tarim were compiled. Research results conclude that the Neogene Miocene developed alluvial fan facies, fan delta facies, and lacustrine facies successively from the piedmont belt to the Maigaiti Slope. During the sedimentation of the Miocene Anju’an Formation, the lake range expanded to its maximum. According to the new division scheme for five-order sequences in prototype sedimentary basin, the stratigraphic sequence of a terrestrial foreland basin was divided and compared, and a sequence development and evolution model was established. Research results show that: (1) the Neogene–Quaternary is a typical type I sedimentary sequence with huge thickness; (2) the Neogene is a period of tectonic compression and flexural subsidence sedimentation in the foreland basin; with the maximum lake flooding surface at the top of the Miocene Anju’an Formation as the boundary, the lower part is a second-order super-sequence of the lacustrine transgression system tracts (TST), the upper part is a second-order super-sequence of the highstand system tracts (HST), and the Quaternary is a second-order super-sequence of the lowstand system tracts (LST) in forced lacustrine regression caused by the Late Himalayan tectonic movement; (3) the classic sequence stratigraphy made an error in establishing the theoretical model of marine type I sequences, as it placed the LST in the wrong position. The corrected type I sequences are in the order of TST, HST, and LST. (4) Finally, two examples were applied to demonstrate the development position of the LST, indicating that whether it is a marine or terrestrial prototype sedimentary basin, the LST was developed during the late stage of tectonic compression and uplift in a basin, and is the sedimentary sequence at the top of the prototype sedimentary basin.