High-resolution sequence stratigraphy of Block 2 in the interior of the Junggar basin

Abstract：Nine key sequence boundaries in Block 2 in the interior of the Junggar basin are traced and ascertained and high-resolution sequence stratigraphic division of the Jurassic was carried out according to the change in sedimentary facies sequence, stacking patterns of parasequences and features of log curves and by using the knowledge of key slope break zones, identifying the basal boundaries of lowstand systems tracts and analyzing onlaps, downlaps and erosional truncations nearby. The study indicates that eight third-order sequences were distinguished in the well C1 area during deposition of the Second Member of the Lower Jurassic Badaowu Formation to Middle Jurassic Toutunhe Formation. Each sequence was characterized by a complete tripartite structure, including lowstand systems tracts (LST), transgressive systems tracts (TST) and highstand systems tracts (HST) from below upward, and 27 systems tracts, 56 parasequence sets and 118 parasequences were identified. The thickness of a single sequence is 105.6-176.8 m and averages 140.7 m；the thickness of a single parasequence set is 24.9 m on the average and the thickness of a single parasequence is 11.8 m on the average.