Distribution and depositional model of microbial carbonates in the Ordovician middle assemblage,Ordos Basin,NW China  

作　　者：WEI Liubin ZHAO Junxing SU Zhongtang WEI Xinshan REN Junfeng HUANG Zhengliang WU Chunying 

机构地区：[1]State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Chengdu 610059,China [2]Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu 610059,China [3]Exploration and Development Research Institute of PetroChina Changqing Oilfield Company,Xi’an 710018,China [4]National Engineering Laboratory for Exploration and Development of Low-Permeability Oil&Gas Fields,Xi’an 710018,China

出　　处：《Petroleum Exploration and Development》2021年第6期1341-1353,共13页石油勘探与开发（英文版）

基　　金：Supported by the China National Science and Technology Major Project(2016ZX05004-006);the CNPC Science and Technology Major Project(2016E-0514).

摘　　要：Based on outcrop profiles,drilling cores,cast thin sections etc.,the types,microfacies combinations and distribution pattern of microbial carbonates in the Ordovician middle assemblage of the mid-eastern Ordos Basin have been systematically analyzed.The middle assemblage of Ordovician in the mid-eastern Ordos Basin has microbial carbonates formed by the calci-fication of cyanobacteria,including microbial biostromes and microbial mounds made of stromatolites,thrombolites,and on-colites.The distribution of the carbonates shows obvious“stratum-control”and“regional”characteristics.The microbial bio-stromes 2–3 m thick each are controlled by sequence cycles and sedimentary facies changes,and were mainly formed in the tidal flat environment during the depositional stages of the Ma56 and Ma55 sub-members.The microbial biostrome in the Ma55 sub-member occurring near the carbonate-evaporite transition interface in the early stage of the transgression is distributed mainly in the Mizhi subsag in the eastern part of the basin;the microbial biostrome in the Ma56 sub-member turns up near the carbonate-evoporite transition zone in ring shape in the east of the central uplift.The ancient landform had noticeable control on the distribution of microbial mounds.The microbial mounds or mound-shoal complexes developing mainly during the de-positional stages of Ma57_Ma510 sub-members are about 15–25 m thick in single layer and distributed largely in the Wushenqi-Jingbian paleouplift.The development model of the microbial carbonate rocks shows that the carbonate-evaporite lithologic transition zone and the Wushenqi-Jingbian paleouplift are favorable exploration zones of microbial carbonates in the Ordovician middle assemblages.

关 键 词：Ordos Basin Ordovician Majiagou Formation microbial carbonates STROMATOLITE thrombolite ONCOLITE deposi-tional model 

分 类 号：P618.13[天文地球—矿床学]