鄂尔多斯盆地西南部晚中生代-新生代盆山转换及构造-沉积响应

Transformation of Basin-mountain Structure and the Tectonic-sedimentary Response in the Southwestern Ordos Basin in Late Mesozoic to Cenozoic

鄂尔多斯盆地是位于华北克拉通西部的一大型多旋回叠合盆地,自晚中生代以来长期处于多个板块汇聚的中心,在盆地不同构造部位也不可避免地发生构造叠加作用和盆山结构的变化。因此准确厘定和恢复鄂尔多斯盆地晚中生代以来的构造活动期次、变形过程和深部动力学是理解东亚地区多板块汇聚的一把关键钥匙,同时也有助于认识盆地内部沉积矿产的关键控矿要素。文章通过解析鄂尔多斯盆地西南部晚三叠世以来的盆-山结构、构造-地层特征、变形和断层的演化序列,结合前人的盆山隆升史和区域动力背景研究成果,系统恢复了鄂尔多斯盆地西南部晚中生代-新生代的盆山演化过程和相应的构造-沉积响应。研究认为早白垩世末—古近纪,鄂尔多斯盆地西南部大部分地区处于夷平阶段,与盆缘具有不同的隆升过程,直至30 Ma以来盆地内部才发生强烈的垂直隆升剥露事件。盆地西南部大量切穿下白垩统的走滑断层为中新世-更新世早期北西向左旋走滑剪切应力作用下形成的不同走滑断层组合,是青藏高原向东北扩展过程中贯入到相对刚性盆地内部的弱应变响应。

Ordos Basin is a significant multi-stage superposition basin situated in the western region of the North China Craton.Over an extended period since the Late Mesozoic,it has experienced substantial plate convergence,resulting in varying degrees of tectonic superposition and changes in the basin-mountain structure across different tectonic units.Thus,the accurate determination and reconstruction of the tectonic activity period,deformation process,and deep dynamics of the Ordos Basin since the Late Mesozoic are crucial for comprehending the multi-plate convergence in East Asia,which will also benefit the understanding of the key controlling factors of deposits in the basin.This paper systematically investigateds the Late Mesozoic-Cenozoic basin-mountain evolution process and the corresponding tectono-sedimentary response in the southwestern Ordos Basin by analyzing the basin-mountain structure,tectonic-stratigraphic features,deformation sequences,and evolutionary patterns of faults since the Late Triassic.Based on the previous studies on the uplift history of the basin-mountain and the regional dynamics background,The study concluded that during the late Early Cretaceous-Paleogene,the majority of the southwestern part of the Ordos Basin was in the planation stage,exhibiting a distinct uplifting process compared to the basin margin.Notably,a significant vertical uplift and denudation of the basin interior occurred since 30 million years ago.Numerous high-angle strike-slip faults in the southwestern part of the basin represent different fault combinations within the same stress context and period since the Late Cretaceous.These faults formed during the Miocene-Early Pleistocene,representing weak strain responses that penetrated into the relatively rigid basin interior during the northeastward expansion of the Tibetan Plateau.