The Cambrian Sequence and Lithofacies Paleogeography in Bachu Uplift in Tarim Basin

Based on the sequence interface identification and sedimentary facies analysis, the Cambrian in Buchu uplift in Tarim basin can be divided into 2 second-order sequences (SS1 and SS2) and 14 third-order sequences. Each second-order sequence consists of transgressive system tract (TST) and highstand system tract (HTS). It is indicated that during the development of SS1-TST, a set of deepwater basin-facies deposit develops in this area with crust subsidence, relative sea-level quick raising; during the development of SS1-HST, the regional sedimentary framework transforms from basin to restricted platform and finally enters into open and evaporating environment influenced by lowing sea level, restricted water cycle and dry-hot climate, dominated by gypsodolomite and gypsite. Thus a set of important regional dense cap rocks is formed; as the development of SS2, a large scale of sea-level ascending-descending cycle occurs, as a result a framework of open platform-restricted platform-open platform is shaped.