鄂尔多斯盆地奥陶系马五5亚段沉积微相与古地理演化

碳酸盐岩微相分析有利于认识沉积相展布特征和古地理演化规律，对油气勘探具有指导意义。通过大量薄片、岩心资料在鄂尔多斯盆地奥陶系马五₅亚段划分出MFT1—MFT7七种沉积微相类型及MA1—MA4四种沉积微相序列，沉积微相与生物遗迹化石指示马五₅亚段为潮坪环境。结合沉积前古地形及古海平面变化信息，以单因素图件为基础，采用优势相法编制马五52层（Ⅰ）、马五51层（Ⅱ）岩相古地理图，沉积环境受沉积前古地形控制而分异:潮上带、潮间上带、潮间下带及潮下带自西向东依次分布，盆地东部高地形处发育潮间带沉积；随古海平面下降，马五51期沉积相带向东迁移，东部潮间带连片分布。

Microfacies and Paleogeographic Evolution of Ma55 Member in the Ordovician,Ordos Basin

Analysis of carbonate microfacies is helpful for understanding the distribution of sedimentary facies and the evolution of paleogeography， which is of guiding significance in oil and gas exploration. Based on a large number of thin-section data and core information， seven types of microfacies （MFT1?MFT7） and four types of sedimentary array （MA1?MA4） were defined in the Ordovician Ma55 member of the Ordos Basin. Microfacies and trace fossils show that the environment of the Ma55 member was a tidal flat. Paleogeographic maps of layers I and II were compiled， indicating that the environments were controlled by the paleotopography: a supratidal zone， an intertidal zone and a subtidal zone occur in sequence from west to east； the intertidal zone was also found in high terrain in the eastern basin. As the sea-level fluctuated， the facies migrated to the east， and the intertidal zone in the east was contiguous.