鄂尔多斯盆地西缘前陆盆地构造-沉积响应

Tectonic-Sedimentary Response of Foreland Basin in Western Margin of Ordos Basin

鄂尔多斯盆地西缘前陆地区在晚三叠世中侏罗世经历了印支运动和燕山运动早期的影响,西缘整体抬升,西南和西北两个造山带开始显现,古地理为继承性的南湖北河格局,此时秦岭造山带的形成使西南地区由滨海相向湖沼相过渡。晚侏罗世早白垩世是西缘地区前陆盆地形成时期,燕山中期逆冲推覆作用强烈,该区地层角度不整合发育,沉积记录的响应表现为南北向隆坳相间的前陆盆地格局,有别于前陆盆地形成始于晚三叠世的认识。晚白垩世新生代是喜山运动的后期改造时期,地层角度不整合发育,沉积响应为平原沼泽相沉积。

The foreland basin in western margin of Ordos Basin experienced the Indo-China movement and the Yanshan movement from early stage of the Late Triassic period to the Middle Jurassic period. During those periods, the western margin was wholly uplifted and orogenic belts appeared in the southwest and northwest. The successive palaeogeographic framework shows that the south part of western margin was lacustrine environment and fluvial environment in the north. The sedimentary facies changed from littoral facies to lacustrine and swamp facies, which was resulted from the forming of Qinling orogenic belt. The foreland basin was formed from Late Jurassic to Early Cretaceous period by strongly thrusting and overriding during the Yanshan movement. There develop angular unconformities in this area. The deposition record indicates the foreland basin framework which is represented by uplifts alternating with depressions. The conclusion is obviously different from that the foreland basin formed in Late Triassic period. The fact that the foreland basin was rebuilt by the Himalaya movement from the Late Cretaceous to Cenozoic period, together with developed angular unconformities and deposition record responses, demonstrates the plain-swamp sedimentary environment.