Study on the Sequence Stratigraphy of the Outcrop of the Cambrian in Danzhai-Sandu, Guizhou

The essay studies the sequence stratigraphy of two Upper-Middle Cambrian outcrops in Danzhai-Sandu, Guizhou, and definitely identified five sequences of three-grade. Among them, there existⅠ-type sequence boundaries either at the top of the Cambrian or in the middle of the Duliujiang formation, the others are Ⅱ-type sequence boundaries. It expounds the tectonic evolution in the area and points out that the depositional environments of two outcrops are changed because of the activities of tectonic fluctuation. Under the control of marine physicochemical condition, the productivity of carbonate rocks and the biological population alter remarkably so as to influence the accumulation process of carbonate platform to a certain extent. Many terms behave as the important control action for the carbonate succession of strata or the distribution and the rank forms of the sedimentary facies in horizontal and vertical. During the Cambrian period, two sediment models in this zones are: 1) broadly open sea shelf type with ramp platform and flat floor, which shaped in early Cambrian; 2) platform (or ramp)-open marine (or basin) sediment model, which formed in upper-middle Cambrian.