Nature, origin and tectonic setting of Jinzhou basin in the south segment of Xuefeng orogen

Abstract：Jinzhou basin is a small NE-trending Late Triassic-Middle Jurassic continental basin in the south segment of Xuefeng orogen. Previous researchers held that the basin is a pull-apart extensional basin related to dextral strike-slipping of NNE-trending Xupu-Jinzhou fault. The authors studied the tectonic characteristics, sedimentary features and proto-basin of Late Triassic-Middle Jurassic Jinzhou basin and, on such a basis, brought forward the opinion that the basin is a compressional quasi-foreland basin according to evidence as follows： ① High maturity of the deposits and the harmony of the basin boundary with surrounding older geological boundary indicates that the basin is a compressional low depression. ② High component maturity and far-resource features of the deposits suggest that the basin was formed in a stable tectonic setting. ③ The sedimentary space of Upper Triassic-Lower Jurassic strata in the northern basin was formed from rocks bending. The attitude changes of rocks indicate that the basin was NW-compressed and folded in Middle Jurassic. Sedimentary features show that there existed shallow- and deep-water environment in the west and the east of the basin, respectively, which implies that the basin was controlled by gravity load of east peripheral thrust block. ④ In adjacent areas of the basin, there occur a few extensional faults and a lot of small strike-slip faults, thrust faults and conjugated shear joints related to the compression. ⑤ According to the strike deflexion of the fault, Jinzhou basin was situated in a compressional area instead of an extensional area when Xupu-Jinzhou fault experienced dextral strike-slipping action. Based on the sedimentary and tectonic characteristics of Jinzhou basin and the regional tectonic setting, the authors hold that the basin was related mainly to regional S-N-compression during Late Triassic-Early Jurassic period, and related to NWW-compression and NNE-trending dextral strike-slipping during Middle Jurassic period.