重塑下哨地区二叠纪岩相古地理

下哨地区处于贵州三叠纪深水槽谷北缘转折部位，岩相古地理变化大。该地区的二叠系主要顺周边展布，中部因三叠系大面积覆盖，仅见下哨与回龙两处露头且出露不全，限制了早期地层的研究深度，尤以下哨二叠系出露区以往的工作程度最低，客观地强化了研究区中部原划二叠纪岩相古地理分布范围的波动性。近期在下哨一带实测的最新资料显示出上二叠统龙潭组含煤岩系连续沉积于下二叠统岜仙组碎屑岩系之上的异相叠积关系，具有区域地层研究意义。据此，本文通过对下哨地区早二叠世茅口期与晚二叠世岩相变化的再认识，重新恢复其古地理格局，并首次提出上二叠统龙潭－长兴组与领组相变的新观念，使晚二叠世深水槽谷相碎屑岩的物源解释更趋合理。

Reconstruction of the Permian Lithofacies and Palaeogeography in Xiashao Area of Guizhou Province

The early study of the Permian strata in Xiashao area, Guizhou, where there is a considerable change in lithofacies - palaeogeography and which is located at the turn of thc northern end of the Permian deep-water trench, is greatly limited owing to a large covering of the overlying Trassic except for only two small and poor outcrops. Thus, the distribution of the Permian lithofacies and palaeogeography originally determined is objectively confused to a large degree.Lately, the data from analysis of a stratigraphic cross-section at Xianhao reveals that the coal measures of Longtan formation in the upper Permian is continuously sedimentated over the detrial rocks of Biaxian formation of the lower Permian in this area. In this paper,a reconstruction of the Permian lithofacies and palaeogeography in this region has been made in terms of the change in lithofacies in Maokou stage of the early Permian and in the late Permian, At final, a conclusion is reached that gives a reasonable explanation for the source of the detrial material deposited in the Permian deep-water trench.