Abstract:

Taizhou Formation in Haian depression of Subei basin developed in Late Cretaceous, the bottom of which was a regional unconformity surface formed by Yizheng movement and the top was a local one by Haian event. There was a regression during its deposition, which divided Taizhou Formation into 2 third-order sequences, named as Sq1 and Sq2. According to the analysis of drilling and core material about 30 wells, both sequences are composed of lowstand systems tract(LST), transgressive systems tract(TST) and highstand systems tract(HST). In Sq1, LST mainly developed braided delta facies, TST developed deep and semi-deep lake facies and HST developed delta facies with decrease of terrigenous detrital material flux  under slow fall of water-level and a lot of turbidite facies. In Sq2, LST developed shallow-shore and semi-deep lake facies, TST developed deep and semi-deep lake facies, HST developed shallow-shore lake facies and strand-bar facies.

Key words: sequence, systems tract, delta, turbidite, Subei basin, Haian depression, Taizhou Formation