雪峰古陆东南侧中、晚泥盆世沉积模式探讨

自古生代到早中生代,一度出现的雪峰古陆,曾在不同程度上影响着川、鄂、湘、黔、桂、赣等省区的沉积岩相及古地理面貌,使古陆两侧面积达数十万平方公里的范围内,沉积了以海相为主的碳酸盐岩和其它多种岩类,反映出多样化的沉积环境。

A PRELIMINARY STUDY OE THE MIDDLE—LATE DEVONIAN SEDIMENTARY MODEL IN SOUTHEASTERN XUEFENG OLD LAND

The Middle-Late Devonian sedimentary model of the southeastern part of Xuefeng old land is of a combined type of old land facies-littoral clastic fa-cies-carbonate platform facie.A comparatively large littoral sea basin once developed in the zone of littoral clastic facies and was filled with large amoun-ts of terrigenous detritus,which provided favorable conditions for the for-mation of the clear-water carbonate platform.Between the zone of littoral facies and that of platform facies,there tends to be a zone characterized bysharp changes of rock facies,the development of which may be related toancient structures and landform.Two small sea basins once occurred on this extensive carbonate platform,the facies of which is different from the basin fa-cies defined by J.L.Wilson,but belongs to the second-order facies on thecarbonate platform.Based on this,the author proposes the concept of the“platform sea basin”.In this paper the carbonate platform is further subdivided into the platform restricted shallow sea and the platform open shallow sea,and a study has been made of the mechanism by which the reefs,reef banks and detrital bea-ches formed on them.The sedimentary model discussed here is to some ex-tent representative of the sedimentary models in the ancient epicontinentalsea in South China.Sedimentary economic deposits such as oil and gas alloccur in a definite facies position of this model.So it is urged that the study of this model should be further strengthened.