Characteristics and Denudation Restoration of Key Unconformities in Lishu Fault Depression

The T4 and T3 were the key unconformities of Lishu Fault Depression.The unconformity T4 represented local inversion structures;T3 was the post-rift unconformity which was a separated depression and fault basin stratum.They represented two inversion structure tectonic movements.Through comprehensively applying two methods of restoring the eroded strata thickness,such as acoustic transit time and vitrinite reflectance,the result shows that erosion thickness of unconformity T4 is about 860~900m,the T3 is about 1100~1480m.Denudation thickness is bigger in the northwest and southeast,and it is less in the southwest.The unconformities T4 and T3 not only could be the important paths for the oil and gas migration,but also are able to be the good places for the hydrocarbon accumulation.