Lower Cambrian sequence-stratigraphic framework of southeastern Guizhou Province

Abstract：Lower Cambrian strata are quite completely developed in southeast Guizhou, and the transitional facies characterized by intense facies change comprise an upward shallowing sedimentary succession, which constitutes a second-order sequence. This second-order sequence can be further divided into five third-order sequences. From northwest to southeast, with the change of sedimentary setting from slope to basin, Lower Cambrian strata gradually thin and eventually form a condensed succession which is difficult to divide in the third-order scale. Based on two kinds of natures of the third-order sequence, i.e., the regularity of lithofacies succession in space and the synchronism of environmental change in time, and taking the two kinds of facies-transition surface and two kinds of diachronisms in stratigraphic records as the fundamental elements in building sequence-stratigraphic framework for the Lower Cambrian strata of the study area, the authors hold that the sequence-stratigraphic framework demonstrates the special third-order sedimentary succession patterns formed after the platform drowning event caused by the rapid transgression at the early stage of Cambrian.