Study On The Meter-Scale Cyclical Sequence And Microfacies Of Ordovician System In Xiaoxian Area

Combined with the principle of sedimentary of carbonate, sequence stratigraphy,lithofacies and paleogeography etc, Xiaoxian was researched in the studying area.According to the information and data we collected in local area, slices analysis and carefully measuring and observation record in Baitu section, we describe characteristic of petrology and the sedimentary structures. We get some conclusions:In the studying area, there are 12 lithology microfacies,and it could be reduced to8 microfacies types:(1) micrites(2) dolomite with calcarenite(3) fine-medium calcarenites(4) dolomitic limestones(5) crystalline dolomites(6) oolitic dolomites(7)calcite dolomites(8) argillaceous dolomite. The major meteoric cycle types in the study area are dolomite-dolomitic limestone-limestone rhythm changes, reflecting the shallow tidal flat. The 5 types of meters scale cyclic are divided, discussed the lithofacies composition and sedimentary environment of each sequence. Single meter scale cycle belongs to sixth cycles, starting with rapid transgression at the bottom of the surface, to form a metre scale shallowing upward sequences. Finally, it is totally have ninethy-two sixth cycles, twenty-three fifth cycles, six fourth cycles, two and a half third cycles are merged from the all the cycles, the paper finally discusses the process and mechanism of cycle evolution of Xiaoxian Ordovician sedimentary profile.