The Basin Structure And Deformation Feature Of The Thrust Belt In The Eastern Cenozoic Foreland Basin Of SW Tarim

The orogenic around Tarim plate has been revived under the collision between Indian plate and Eurasian plate since Cenozoic. It formed a broad thrust belt at the joint between the mountain and basin because of the violently extrusion. The inner part of the basin fleexed strongly to generate a foreland basin. By the analysis of the tectonic deformation of the thrust belt and the sedimentary characteristics at the inner basin, we can clarify the evolution of the Tarim foreland basin, and it can reveal the evolution of the adjacent orogenesis.Combining the eismic data, drilling data and field observation with the hermochronology data from predecessors, the structure of basin-mountaintectonics, deformation features of the thrust belt and filling characteristics can be revealed as follows:(1) According to the division of foreland basin tectonic units, the Tarim forelandbasin can be divided into northern west Kunlun orogenic belt, Kedong tectonic zone, Yecheng depression, Maigaiti slope and Bachu uplift. The thrust belt is characterized by rows of fault-related folds, which includes Kedong-anticline belt, Kekeya-anticline belt, Guman-anticline belt and Jiede-anticline belt. At the foreland depression, it subsided smoothly, and the abundant source contributed to a thick cenozoic deposition. The slippage effect of the salt layer made the thrust propagate into the inner basin, which caused the thrust belt overlapping with the depression. And now, the forward of the fold thrust belt has spreaded along the Jiede anticline. At the slope, the sediment formed a wedge from south to north. Controlled by the thrusts of both sides, Bachu developed to an inheritance forebulge. Affected by the detachment layer and the wedging of Pamir, the basin structure differs. It developped to a basement-involved structure near the orogenic and a thin skinned structure in the inner basin.(2) The fold-and-thrust belts have suffered amulti-phase tectonic events. In the early Pliocene, it formed the first row of anticline because of the SN trending compressional stress. From the late Pliocene to Pleistocene, the structural belt was transformed by the Fusha-Keliyang fault. In the west, the fault cut through the north wing, and showed a thrust-slip structure. In the middle,the fault cut through the core of the anticline, and formede a "flower structure", which indicated a strike-slip tectonic deformation. While in the east, the fault cut through the north wing, and showed a thrust structure. According to the structural characteristics of the section, the piedmont tectonic belt can be divided into Pudong zone, Yuliqun zone and Keliyang zone from west to east.(3) The sedimentary characteristics of the Fusha2-Jiede1well logs display the evolution of the foreland basin. The foreland basin started at N1k, The fine silt showed that the fold and thrust belts were in the farther south than today. During N1a-N1p, it gets rough from south to norht, which indicates a provenances supply from the north. The foreland basin was in a quiet evolution. At N2a, the gravel spreads widely in the basin, indicating a severe orogenesis. The tectonic activity has propagated to the inner basin, and the basin was at its boom. The shifting low of the growth strata made it clear that the thrust belt started from N2a. And it formed the setup at Pleistocene.