摘要： 在系统收集陕北地区中侏罗统延安组野外露头、钻井、测井、古生物等资料的基础上，对延安组沉积期的沉积环境及其层序地层格架进行分析，并恢复了各层序沉积期的岩相古地理格局。将延安组划分为3个三级层序，分层序绘制了关键单因素的等值线图，恢复了各层序沉积期的岩相古地理格局。层序Ⅰ沉积早期主要为河流沉积；随着盆地沉降的加剧，中部地区逐渐变为湖泊沉积，东北部河流沉积演变为三角洲沉积；层序Ⅱ沉积时期基本继承了层序Ⅰ晚期的沉积格局，古地理格局相对较稳定；层序Ⅲ沉积期，盆地基底不断抬升，湖泊逐渐萎缩成局限湖，河流沉积、三角洲沉积分别在研究区中部、东北部大规模发育。

关键词: 沉积相, 层序地层, 古地理, 延安期, 陕北地区

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.

Key words: sedimentary facies, sequence stratigraphy, palaeogeography, Yan′an Age, northern Shaanxi Province

中图分类号: 

• P531