Two stages of subsidence and its formation mechanisms in Mid-Late Triassic Ordos Basin,NW China  

作　　者：DENG Xiuqin CHU Meijuan WANG Long CHEN Xiu WANG Yanxin 

机构地区：[1]National Engineering Laboratory for Exploration and Development of Low-Permeability Oil&Gas Fields,Xi’an 710018,China [2]Exploration division of PetroChina Changqing Oilfield Company,Xi’an 710018,China [3]Exploration&Development Research Institute of PetroChina Changqing Oilfield Company,Xi’an 710018,China

出　　处：《Petroleum Exploration and Development》2024年第3期576-588,共13页石油勘探与开发（英文版）

基　　金：Supported by the National Science and Technology Major Project(2017ZX05001);CNPC Science and Technology Project(2021DJ22).

摘　　要：Based on a large number of newly added deep well data in recent years,the subsidence of the Ordos Basin in the Mid-Late Triassic is systematically studied,and it is proposed that the Ordos Basin experienced two important subsidence events during this depositional period.Through contrastive analysis of the two stages of tectonic subsidence,including stratigraphic characteristics,lithology combination,location of catchment area and sedimentary evolution,it is proposed that both of them are responses to the Indosinian Qinling tectonic activity on the edge of the craton basin.The early subsidence occurred in the Chang 10 Member was featured by high amplitude,large debris supply and fast deposition rate,with coarse debris filling and rapid subsidence accompanied by rapid accumulation,resulting in strata thickness increasing from northeast to southwest in wedge-shape.The subsidence center was located in Huanxian–Zhenyuan–Qingyang–Zhengning areas of southwestern basin with the strata thickness of 800–1300 m.The subsidence center deviating from the depocenter developed multiple catchment areas,until then,unified lake basin has not been formed yet.Under the combined action of subsidence and Carnian heavy rainfall event during the deposition period of Chang 7 Member,a large deep-water depression was formed with slow deposition rate,and the subsidence center coincided with the depocenter basically in the Mahuangshan–Huachi–Huangling areas.The deep-water sediments were 120–320 m thick in the subsidence center,characterized by fine grain.There are differences in the mechanism between the two stages of subsidence.The early one was the response to the northward subduction of the MianLüe Ocean and intense depression under compression in Qinling during Mid-Triassic.The later subsidence is controlled by the weak extensional tectonic environment of the post-collision stage during Late Triassic.

关 键 词：Ordos Basin Chang 10 Member Chang 7 Member subsidence center depocenter subsidence mechanism Qinling orogenic belt Indosinian movement 

分 类 号：P618.13[天文地球—矿床学]