Palaeogeographic characteristics of the Middle Jurassic Yan′an Age in northern Shaanxi Province
Wang Dongdong1, Shao Longyi1, Li Zhixue2, Li Zhaobin1
1 College of Geoscience and Surveying Engineering，China University of Mining and Technology(Beijing)，Beijing 100083 2 Investigation Academy of Shaanxi Coalfield Geology Bureau，Xi′an 710054，Shaanxi
Abstract：This paper systematically collected some basic data including outcrops， wells，loggings，paleontological data， etc. Based on those data，the sedimentary environments and sequence stratigraphic framework of the Middle Jurassic Yan′an Formation were analyzed，and the lithofacies palaeogeography map of each sequence was drawn.In this paper，the Yan′an Formation can be divided into 3 third-order sequences and taken as the drawing unit.Based on this，some key single factors isoline maps were drawn.By analyzing all the single factors synthetically，the lithofacies palaeogeographic maps of each sequence were reconstructed.During the early depositional period of the sequence Ⅰ，the fluvial deposits were developed.Then，the basin sedimentation aggravated，the deposits of the basin center gradually changed into lacustrine deposits. The sedimentary framework of the sequence II basically inherited that of the late period of sequence Ⅰ，and the palaeogeographic patterns were relatively stable.During the depositional period of sequence Ⅲ，the basin basement continuously lifted，the lake gradually changed into limited lake，and the fluvial and the delta deposits were mainly developed in the middle and northeastern area of the study area respectively.
Wang Dongdong,Shao Longyi,Li Zhixue et al. Palaeogeographic characteristics of the Middle Jurassic Yan′an Age in northern Shaanxi Province[J]. JOPC, 2012, 14(4): 451-460.
