Abstract:

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.