RECOGNITION OF SOFT SEDIMENTARY DEFORMATION STRUCTURES FROM EDIACARAN TO CAMBRIAN IN THE AKSU AREA (NW TARIM BASIN, CHINA) AND ITS GENETIC ANALYSIS

The Tarim Basin, which is the largest continental and marine superimposed basin of the northwestern part in China, has been considered as a stable intracratonic sag basin during the Ediacaran to the Cambrian. Undeformed and marine deposition environment were thought the main tectonic-sedimentary characteristics. In this study, various types of soft-sediment deformation structures (SSDS) are recognized on the multiple outcrop sections in the Aksu area, NW Tarim basin. They include the load cast, liquefied breccia, liquefied doloarenite wedge, mound and sag, boudinage-like structures, convolutes, sliding slump and folds. Deformation layers are composed of interbedded thin black shale and phosphorite chert layers, thick-bedded shallow gray dolomite and silicalite layers in the Yurtus Formation of the Cambrian, while the dark grey dolomites with gray dolomite or grayish green mudstone layers in the Qigebulark Formation and the brown sandstone layers in the Sugaitbulark Formation of the Ediacaran, respectively. They developed in the deep sea, shelf, carbonate platform and onshore depositing environments. Combined to the regional tectonic framework and activities, the spatial-temporal distributions and formation mechanism of SSDS are analyzed and discussed. We propose that the SSDS layers could form to correspond to different events, such as a regional unconformity, a sub-stratigraphic sequence interface, high magnitude earthquake events and lithology configurations; they are the excellent records for the related high-resolution paleo-tectonic active events in the main tectonic movement.