贵州东南部下寒武统层序地层格架
Lower Cambrian sequence-stratigraphic framework of southeastern Guizhou Province
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摘要: 提要：贵州东南部下寒武统发育较为完整，相变剧烈，组成总体向上变浅的沉积序列，该序列代表一个二级层序；该二级层序还可以进一步划分为5个三级层序。自北西向南东，随着从斜坡到盆地的沉积背景变化，下寒武统逐渐变薄，直至变为一个难以进行三级层序划分的凝缩作用序列。依据三级层序“空间上相序的有序性和时间上环境变化的同步性”，以地层记录中“两种相变面和两种穿时性”为基本要素建立研究区下寒武统层序地层格架，该格架表明了在寒武纪早期的快速海侵所造成的台地淹没事件之后，所形成的特殊的三级沉积序列样式。Abstract: 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.
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