上扬子区下寒武统的层序地层格架及其形成的古地理背景

现代地质 ›› 2006, Vol. 20 ›› Issue (2): 195-208.

上扬子区下寒武统的层序地层格架及其形成的古地理背景

梅冥相^1,2，张丛^1,2，张海^1,2，孟晓庆^1,2，陈永红^1,2

1. 中国地质大学地质过程与矿产资源国家重点实验室，北京100083；
2. 中国地质大学岩石圈构造、深部过程及探测技术教育部重点实验室，北京100083

收稿日期:2005-11-20 修回日期:2006-01-15 出版日期:2006-02-20 发布日期:2006-02-20
作者简介:梅冥相，男，教授，博士生导师，1965年出生，沉积学与地层学专业，主要从事沉积学与地层学的研究工作。
基金资助:
中国石化科技工程重点项目（QZ-2005-06）

Sequence-Stratigraphic Frameworks and Their Forming Backgrounds of Paleogeography for the Lower Cambrian of the Upper-Yangtze Region

MEI Ming-xiang^1,2, ZHANG Cong^1,2, ZHANG Hai^1,2, MENG Xiao-qing^1,2, CHEN Yong-hong^1,2

1. State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Beijing100083, China；
2. Key Laboratory of Lithosphere Tectonics and Lithoprobing Technology of Ministry of Education, China University of Geosciences, Beijing100083, China

Received:2005-11-20 Revised:2006-01-15 Online:2006-02-20 Published:2006-02-20

摘要/Abstract

摘要：

上扬子区特别是贵州及邻区的下寒武统发育完整，是一套从黑色页岩系到碳酸盐岩的地层序列，该序列构成一个复杂而有序的层序地层格架。在时间变化方面，下寒武统组成一个二级层序，其中可以进一步划分为5个三级层序，形成一个有序的海侵—海退旋回序列；在二级层序之中，三级层序形成一个有序的垂直叠加形式，自下而上三级层序由“凝缩段（CS）+高水位体系域（HST）”序列演变为“海侵体系域（TST）+凝缩段（CS）+高水位体系域（HST）”，层序界面类型由淹没不整合型层序界面演变为明显的暴露间断面，意味着二级层序的相序组构与三级层序存在相似性。在空间变化方面，从北西向南东随着古地理背景由浅变深，下寒武统厚度变薄，向东南变为一个难以进行三级层序划分的凝缩序列。该层序地层格架不但表明了三级层序的两大属性——“空间上相序的有序性和时间上环境变化的同步性”，而且反映出地层记录中“两种相变面和两种穿时性”。同时，所建立的层序地层格架表明了其复杂的古地理背景；具有不同特点的三级层序代表了不同的古地理背景，意味着早寒武世复杂的古地理变迁。因此，系列层序地层格架栅状图反映出每一个三级层序的相序组构的时空变化，而系列古地理图又代表了各个三级层序形成时期的独具特色的古地理背景。

关键词: 上扬子区, 下寒武统, 层序地层格架, 古地理背景

Abstract:

In the Upper-Yangtze region, especially in Guizhou Province and its adjacent areas, the Lower Cambrian is well developed and is marked by a succession from black shale to carbonate rocks. And this stratigraphic succession makes up a complex and regular sequence-stratigraphic framework. The Lower Cambrian in the study area constitutes a second-order sequence that can be further subdivided into five third-order sequences, and form a regularly cyclic succession of the transgression-regression. There is a regularly vertical stacking pattern for the third-order sequence in the second-order sequence. From the bottom to the top, third-order sequences that are characterized by the succession of “the CS (condensed section) +HST (high-stand system tract)” are changed into those marked by the succession of “the TST (transgressive system tract)+CS+HST”, correspondingly, the drowning-type sequence boundary is changed into exposure-type one. Therefore, both the second-order and the third-order sequences have a similarity of sedimentary-facies fabric. A concomitant with these temporal changes is that the Lower Cambrian containing five third-order sequences with 1,000 meter thickness is changed into a condensed succession that third-order sequences can not be identified toward the southeast with the deepening of the sedimentary environment. The sequence-stratigraphic framework can demonstrate both the elementary features of the third-order sequence, i.e. the regularity of sedimentary-facies successions in space and the synchronism of sedimentary-environment changes in time, and two kinds of facies-changing surfaces as well as two kinds of diachrononism in the stratigraphic records. And the sequence-stratigraphic framework represents its complex forming-setting of palaeogeography. Third-order sequences with different facies-succession mean particular paleogeographic backgrounds; therefore, five third-order sequences of the Early Cambrian represent a complex paleogeographic variance in the study area. Ultimately, a series of the panel diagrams of sequence-stratigraphic framework shows the temporal and spatial changes of sedimentary-facies succession of the third-order sequence, and a series of the corresponding paleogeographic maps indicates the evolution of paleogeographic setting that forms the third-order sequences.

Key words: the Upper-Yangtze region, the Lower Cambrian, sequence-stratigraphic framework, paleogeographic background

中图分类号:

P539.2

梅冥相张丛张海孟晓庆陈永红. 上扬子区下寒武统的层序地层格架及其形成的古地理背景[J]. 现代地质, 2006, 20(2): 195-208.

MEI Ming-xiang, ZHANG Cong, ZHANG Hai, MENG Xiao-qing, CHEN Yong-hong. Sequence-Stratigraphic Frameworks and Their Forming Backgrounds of Paleogeography for the Lower Cambrian of the Upper-Yangtze Region[J]. Geoscience, 2006, 20(2): 195-208.

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