皖西白大山群的发现及其地质意义

THE DISCOVERY OF THE BAIDASHAN GROUP IN WEST ANHUI AND ITS GEOLOGICAL SIGNIFICANCE

皖、豫交界的白大山－茶庵一带，出露一套碎屑岩夹碳酸盐岩地层，以往被置于青白口系八公山群。近期笔者等赴该地再次进行了调查和研究，结果发现该群地层组合内含有大量球藻类和植物碎片化石，这些微古植物分子在国内外多见于下古生代。并从岩石组合特征对比分析，认为该套地层属志留－泥盆系的可能性最大。对这套地层及微古植物的发现，具有两方面重要的地质意义：１．过去对华北地台南缘从未见有这个时代地层的报导，这就为该区地层填补了一个空白；２．从已采获的微古植物组合及岩性组合特征等分析，这有可能对华北地台南缘的岩相古地理图及地史发展等问题，进行一些必要的改写与补充。

In the Baidashan-Chaan area, a junction area of Anhui and Provinces, a suite of clastic rocks in-tercalated by carbonate rocks in outcropped, which was classified into the Bagongshan Group of the Qingbaikou System in the past. After further investigation and study, the author in the mentioned strata discovered a lot of spherical algae and phytoclast fossils which are usually found in lower palaeozoic strata both at home and abroad. Together based on the cor-relation analysis of rock association, the author holds that the strata most possibly belong to the Silurian-Devonian.The discovery are of important geological significance in two aspects: 1.The Silurian and Devonian strata have never been found in the south margin of the North Chine plate , so the studied strata filled up a stratigraphic blank in thisarea. 2. The new discovery may lead to a necessary revision or supplementation of the lithofacies- palaeogeographicalmap of the south margin of the North China plate and other data such as its geological history.