DISTRIBUTION OF THE QUICK SUBSIDENCE CENTERS AND TECTONIC CONTROL ON THE JURASSIC XISHANYAO FORMATION IN JUNGGAR BASIN

Based on the 329 data points that were acquired from 21 regional seismic profiles in Junggar Basin, the subsidence history of the Jurassic Xishanyao Formation strata was analyzed with the EBM basin modeling system. The backstripping results indicate that the subsidence rate of the basin displays remarkable inhomogeneous changes in different times and different areas. The subsidence rate for this basin is 70~90 m/Ma in the southern part during the sedimentary stage of the second member of the Xishanyao Formation, but is only 30 m/Ma in the northern and central regions of the same basin. The subsidence rate for the southern part in this basin reaches 120 m/Ma during the sedimentary stage of the first member of Xishanyao Formation, and the subsidence rates for the northern and central regions remain stable when compared to that for the second member of the same formation. Based on these results, the three quick subsidence centers, i.e., Mahu, Wulun and Changji depressions, during the sedimentary periods for the Xishanyao Formation in Junggar basin, can be identified, and the Changji depression in the southern part of the basin proves to show the maximum subsidence rate. The formation of these quick subsidence centers were obviously controlled by the tectonic load derived from the adjacent orogenic thrusting and preexisting tectonic blocks in the basin basement. The quick subsidence centers are the important areas for the lowstand delta sand body development, and can provide information for exploration of the subtle trap reservoirs.