鄂尔多斯盆地东北缘晚古生代陆表海含煤岩系层序地层研究

Sequence Stratigraphy of Late Paleozoic Coal-Bearing Measures in Northeastern Ordos Basin

通过区域不整合面、沉积体系转换面、构造应力场转换面和水上暴露面等层序界面的识别,对研究区进行层序地层划分,指出鄂尔多斯盆地东北缘晚古生代陆表海含煤岩系发育7个三级层序。在此基础上,认为陆表海层序仍然具有"三元"结构,由低位体系域、海侵体系域和高位体系域组成。在盆地北部发育的多期河道砂岩具有低位体系域的下切谷充填特点——面状充填,如晋祠砂岩、桥头砂岩以及北岔沟砂岩等。煤层在层序格架中的定位与海平面变化的转换时期有关,主要发育在陆表海环境的海侵体系域下部以及陆相环境的高位体系域上部。

By the identified the regional unconformity, sedimentary system conversion, tectonic stress conversion and exposed surface, the authors divided the Late Paleozoic coal-bearing measures in northeastern Ordos basin into seven 3rd sequences. Based on the study, the ternary texture of epicontinental sequence indicate that they also consist of lowstand systems tract, transgressive systems tract and highstand systems tract. Some fluvial sandbodies developed in the northern Ordos basin characteristic by filling of valley-incised in the lowstand systems tract that is sheet sandstone such as Jinci sandstone, Qiaotou sandstone and Beichagou sandstone. The position of coal seams in the sequence framework has relationship to the transformation time of sea level change, and develops mainly at the lower part of transgressive systems tract in epicontinental sequence and the upper part of highstand systems tract in nonmarine sequence.