鄂尔多斯盆地西缘石沟驿地区晚三叠世沉积构造环境及其地质意义

Geological environment of Upper Triassic sediment in Shigouyi region of western Ordos Basin and its geological significance

对鄂尔多斯盆地西缘晚三叠世大地构造环境和区域应力场与石沟驿地区上三叠统沉积速率、碎屑组分和盆地充填样式等构造环境判别的综合分析,认为晚三叠世石沟驿地区为逆冲挤压构造环境,冲断带挤压挠曲作用形成前陆前渊拗陷,物源区为再旋回活动的褶皱冲断带。与典型前陆盆地相比,位于冲断带前缘的鄂尔多斯盆地为具石沟驿等前渊拗陷的类前陆盆地。晚三叠世石沟驿地区逆冲挤压和六盘山地区整体隆升的构造背景揭示,牛首山—罗山一带的西缘逆冲带构成晚三叠世鄂尔多斯原型盆地的西南部边界,石沟驿地区上三叠统是盆地延长组边缘相沉积。上述认识有助于扩大鄂尔多斯西缘中生界和古生界的油气勘探远景。

The integrated analysis of the tectonic setting and regional stress field in western Ordos Basin and the rate of sedimentation, clastic composition and sedimentary filling shape in Shigouyi region in Late Triassic shows that the west margin of the Ordos Basin in Late Triassic was in overthrust-compression structural environment. The foredeep depression was formed by the compression function of foreland overthrust belt, and its provenance was the recycled fold-thrust belt. Compared with typical foreland basins, the Ordos Basin, in front of the thrust belt, is a quasi-foreland basin. The overthrnst-compression in Shigouyi and the uprising in Liupanshan reveal that the foldthrust belt in Niushoushan-Luoshan is the southwest boundary of the Ordos prototype basin in Late Triassic and the Upper Triassic sediment in Shigouyi region is of the margin of Yanchang Formation of the Ordos Basin. The new recognigation is beneficial to indicate more prospects of petroleum exploration in Mesozoic and Paleozoic in the west margin of the Ordos Basin.