试论宁夏地区始新统寺口子组沉积的构造背景

做为新生代宁夏境内的第一套沉积，始新统寺口子组具有其特殊的意义，但一直没有得到满意的解释。从寺口子组的沉积规模以及较为剧烈的沉积相变化来看，寺口子组的沉积来的很突然。通过沉积相以及构造分析表明寺口子组是走廊南山前陆盆地中前隆位置靠前陆盆地一侧的沉积。该盆地是30～40Ma之间走廊南山逆冲隆起的前陆盆地，盆地的前隆沉积单元位于鄂尔多斯西缘及香山等地区，隆后沉积单元位于鄂尔多斯西缘以东，由于挠曲作用在该前隆上产生了许多倾向造山带的正断层，这些正断层控制了寺口子组的分布．基本上是一种近源的快速堆积，形成一系列围绕前隆的冲积扇或洪积扇沉积，物源为鄂尔多斯西缘隆起等地区。

Discussion on the Tectonic Setting of Deposition of the Eocene Sikouzi Formation in Ningxia Region

As the first sediment in Cenozoic time in Ningxia region, the Eocene Sikouzi Formation has special tectonic meaning, however, its development has not been interpreted satisfactorily yet. From the point of deposition scope and more radical change of sedimentary facies, the Sikouzi Formation occurred abruptly. By the means of facies and structural analysis, the authors think that the Sikouzi Formation was deposited on the forebulge facing to the Corridor Nan Shan which resulted in the development of one foreland basin 30-40 Ma ago, the forebulge unit of this foreland basin was located along the western margin of Ordos Basin and Xiangshan area, the back-bulge unit lay to the east of western margin of Ordos Basin. Because of flexing, many normal faults dipping to the orogen came into being on the forebulge, it was these normal faults that controlled the distribution of Sikouzi Formation which was deposited rapidly and formed a serial of alluvial fans around forebulge, the provenance of it was the uplifts along the western margin of Ordos Basin and Xiangshan area, etc.