关键词: 准噶尔盆地, 不整合, 剥蚀厚度, 参考层序厚度, 恢复方法

Abstract: A new method for restoration of eroded strata thickness by ratios of reference sequence strata thickness(RRSST)was proposed and used to restore the thickness of eroded strata in the Cretaceous/Jurassic(K/J)unconformity in the hinterland of Junggar Basin. The new method is based upon the similarity distribution of sequences strata thickness under similar tectonic and depositional environment. The restoration steps are as follows. First, the sequence boundaries were plotted on the seismic sections, and the thickness of single sequence was got out according to time-depth conversion. Second, the single sequence or multiple sequences underlying the K/J unconformity with no erosion and small variation range of sequences strata thickness were taken as reference sequences. Third, the distribution of RRSST when erosion just began to happen was modeled using eroded strata thickness and thickness of sequence strata in single well. Last, the eroded strata thickness was worked out using the modeled RRSST, the strata thickness of the reference sequences and the strata thickness from the bottom of the reference sequences to the eroded surface at present. Calibration of restored eroded strata thickness could be made according to geological model. The restoration shows that the eroded strata thickness is from 300 meters to 800 meters in the west part of Junggar Basin and below 300 meters in the east part of the basin. The method can be widely used in large area with few wells and low level of recognitions.

Key words: Junggar Basin, unconformity, eroded strata thickness, strata thickness of reference sequence, restoration method