宁东地区延安组高分辨率层序地层分析

High-resolution Sequence Stratigraphy of Yan′an Formation in Eastern Ningxia

宁东地区位于鄂尔多斯盆地西缘构造带,中生界侏罗系延安组是主要含煤地层,而其高分辨率层序地层划分仍然不清。通过对露头、岩芯、测井资料以及延安组沉积体系与构造演化的详细研究,进行层序界面的识别,建立等时层序地层格架并进行高分辨率层序地层划分。研究表明,宁东地区延安组可划分为一个超长周期旋回、4个长周期旋回、11个中期基准面旋回、至少25个短期基准面旋回。

The eastern Ningxia area is located at the west margin structural belt of the Erdos basin.The Yan′an formation of Jurassic system,Mesozoic Erathem contains the main coal-bearing strata.However,its high-resolution sequence stratum division is still unclear.Through the detailed study of outcrops,core and logging data as well as the sedimentary system and tectonic evolution of Yan′an formation,this paper made the identification of sequence interface and set up the isochronic sequence stratum framework and divided the high-resolution sequence strata.The research showed that the Yan′an formation in eastern Ningxia could be divided as a super long-periodic cycle,4 long-periodic cycles,11 mid-periodic base-level cycles,and at least 25 short-term base-level cycles.