Dynamic Stratigraphy of Lower and Middle Collbrian in Western Hunan and Eastern Guizhou

By using graphic analysis to study carbonate and terrigenous clastic sediments of the western Hunan and eastern Guizhou provinces, the different dynamic factors uneiital carbonate sequences in this area are studied especially. With the analysis, the ooidalpisolitic grainstone, oncolitic packstone and intraclastic gram and tidal dominated environments are discussed.Furthermore, the characten and gravity flow sediments are analyzed, and the sedimentary mechanics of st is idscussed. Particularly, the authors studied the hummocky cross-stratifie in tempestite sequence. Which was to be the product of unidirectional back-flow of gradient current- formed by storm interpays with storm wave action, this bed-form is a transitional type betwwen syn ripples with straight crest and the upper flat bed- form of gradient currents.Pale rent sis of Cambrian contour currents in studied area indicates the paleocurrent flown from NE to S and along the edge of the basin. Four ki difterent veruend es are recognized, which includes the shallowing-upward cycles, and minor" transgoressive regressive pulses. Lateral distribution of facies may indicates paleogeograp ter diferent periods: a gentle slope consists of algal mound during the early Cambrian and a steep slope consists of ooidal shoal in the middle Cambrian.The sedimentary dynamics of the mentioned slope is suggested: (1) wavy and tidal action that affected the shore belt; (2) storm events that influenced the shore and shelf environments; ( 3) sliding and gravity flow that developed across to the shoreline; (4) contour current that flowed along the slope and parallelled to the shoreline. Comparision of minor cycles suggests that the dynamic factors controlling these cycles may be derived from the block faulting. The regressive sequence of basinal edge was controlled by the.interaction of plate spreading, sealevel changing and the developing of carbonate itself.