十万大山盆地中生代沉积充填特征及其演化

十万大山盆地是印支期以来发展起来的中、新生代陆相盆地。盆地自晚三叠世-白垩纪具有比较典型的碰撞前陆盆地特征。该时期盆地的地层、沉积相类型及时空展布、沉积旋回和沉积边界的迁移具有明显的规律性。盆地的沉积地层多以山麓相、河流相为主，尚有少量滨浅湖相沉积，具近物源沉积特征；沉积相展布自晚三叠世至白垩纪具有沉积范围小-大-小-大的规律；沉积旋回呈现了浅-深-浅的规律；沉积边界和沉降中心不断向北和北东方向迁移。这些规律反映了十万大山前陆盆地的构造演化，即晚三叠世碰撞逆冲活动启动，盆地进入前陆盆地发育阶段；早、中侏罗世造山活动强烈，盆地沉降幅度大，物源供应充足；晚侏罗世造山活动减缓，盆地相对萎缩；白垩纪造山活动再次加强，盆地处于第二个发育期。

Sedimentary filling of Shiwandashan Foreland Basin and its evolution

The Shiwandashan Basin in Guangxi Province,South China,is a foreland basin developed from Late Triassic to Cretaceous. The distribution of strata,sedimentary facies,and sedimentary cycles as well as migration of sedimentary boundaries show regular variations. Deposits of the basin are dominated by alluvial and fluvial facies,while lacustrine facies are of secondary,which reflects close provenance for these fillings. The sedimentary cyclicity is from shallow to deep,and then to shallow again. The sedimentary boundaries and deposition centers moved northward or northeastward. All of these are reflections of the tectonic evolution of Shiwandashan Basin. In Late Triassic,collision of Shiwandashan orogen started,resulted in the formation of the foreland basin. In Early and Middle Jurassic,as orogenic activity intensified,the basin subsidence increased and it sediment supply was sufficient. In Late Jurassic,as the orogenic activity slowed down,the basin became smaller than before. In Cretaceous,while the orogenic activity strengthened once more,the basin was in the second developing period.