The Evidences of Diagenetic Environments and Diagenetic Sequences of Grainstones

This paper deals mainly with oolitic limestones in the Zhangxia Formin the Tangshan area and other places. On the basis of the evidences of diagcnctic enviromas characteristics of cementation, the occurrence of dolomites, syntarial overgrowth of and micritization, it has been proposed that diagenetic sequences of the grain sediments dwith distinct sedimentary microenvironments, resulting in the occurrence of predictable superimposed diagenetic evidences and the understanding of the evolutionary law of the porosity. It is emphasized in the latter part of the paper that the grain cements are not only restricted to sparry calcite but also include the micritic cements in ncarshore environments. The microfcatures represented by both of them are obivously distinct.