Abstract:

Upper Triassic Riganpeicuo Formation in Gaize area, Tibet, developed a set of platform facies carbonate sediments which are a characteristic of multi-layer oolitic beaches, and these multi-layer oolitic beaches could be further divided into open platform shoal and platform margin beach.Analysis of rock types showed that this set of carbonate sedimentary succession was formed in the fringe platform sedimentary environment and the intraplatform shoal developed melange of in situ and allogeneoolitic oolitics, while the platform margin beach developed mainly in situ oolitic. Platform margin oolitic beach was a subsequence of progradational sequences in three-order transgressive system tract, and had characteristics of subtidal type meter-scale cyclic. Each oolitic limestone layer was relatively single in type and uniform in size, and the oolitic type was different among the oolitic limestone layers which possessed the trend of changes from omicrite to radial, and to concentric ooides. The size of oolitic increased and sedimentary thickness increased markedly from lower to upper.