豫西地区晚三叠世盆地原型探讨

Prototype of Late Triassic basin in Western Henan

豫西地区上三叠统与西部鄂尔多斯,南部北秦岭地区晚三叠世具有较好可对比性,岩性都以暗色细、粉砂岩与泥页岩互层为主,均未出现粗粒边缘相沉积;豫西地区上三叠统厚800~2000m,呈现东北薄、西南厚的变化趋势,与鄂尔多斯地区西北薄东南厚的特征相吻合;洛阳、义马等凹陷上三叠统分布稳定,均未出现楔状减薄尖灭,明显有别于小型断陷盆地;现今隆起均形成于燕山期以后,晚三叠世不存在大的分割构造。因此,豫西地区与鄂尔多斯盆地在晚三叠世应为一连通的大型沉积盆地。

The upper Triassic series in Western Henan are identical to late Triassic epoch in Western Ordos,North Qinling Mountain,where the lithology are dominated by dark,fine siltstone and shale interbeds,and no coarse facies occur;The upper Triassic series in Western Henan range from 800 to 2000 m,representing the trend of northeast thin and southwest thick,which is consistent with the characteristics of Ordos. The upper Triassic series in Luoyang and Yima sag distribute stably,there was no wedge thinning and pinching,which is significantly different from the small faulted basin. The uplift was formed after Yanshan period,there is no big structural segmentation in late Triassic epoch. Therefore,the western Henan and Ordos basins should be connected as large sedimentary basins in the late Triassic epoch.