Segmentations of foreland belts and their tectonic mechanism in the Southwest Tarim Basin

Abstract

Based on lots of field investigations and comprehensive interpretations of seismic profiles with outcrop cross-sections, this paper shows that the foreland belts surrounding the Southwest Tarim Foreland Basin have the regularity of segmentation along the strike of foreland belts. There are many thin-skinned thrusting systems thrusting from mountains to the basin and the arcuate back-thrusting systems to the mountains distributed at intervals in the front of West Kunlun-Pamir and Southern Tianshan. Between thrusting and back-thrusting systems, the strike-slip faults developed. The northeast uplifts and depressions of Southwest Tarim Basin correspond with the segmentation of foreland basin. The thin-skinned thrusting system is formed in the case that the thickness of sedimentary covers is less than 10 km in depth where the basement is an uplift belt in general. The back-thrusting systems and triangle zones are formed in the case that the thickness of sedimentary covers is larger than 8 km in depth where the basement is a depression zone. The main mechanics of segmentation of foreland basin are the difference of mountain uplift and deformation rate along the longitude of the mountains, the huge sedimentary rocks in different depression centers, the uplift belts and depression zones in the basement rocks, and multi-displaced weak layers in the foreland basin. The segmentation of Southwest Tarim Foreland Basin is due to the intra-plate deformation of re-orogenies of West Kunlun-Pamir and Southwest Tianshan and the co-related deformation between mountains and basement of basin since Neocene.