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湖北兴山古洞口剖面中-上寒武统白云岩特征及其古环境意义

ISSN号：1671-1505
期刊名称：《古地理学报》
时间：0
分类：P581[天文地球—岩石学;天文地球—地质学]
作者机构：[1]北京大学地球与空间科学学院,北京100871, [2]中国石化集团国际石油勘探开发有限公司,北京100029, [3]造山带与地壳演化教育部重点实验室(北京大学),北京100871, [4]中国科学院现代古生物学和地层学国家重点实验室,江苏南京210008
相关基金：国家自然科学基金项目（编号：40972020,41272035,41221001,41290260）和现代古生物学和地层学国家重点实验室共同资助

关键词：上扬子区, 中-上寒武统, 白云岩, 沉积环境, Upper Yangtze Region, Middle-Upper Cambrian, dolostones, sedimentary environments

中文摘要：

华南上扬子区中部中-上寒武统白云岩大量发育，形成于特殊的古气候、古海洋环境，但其沉积环境和成因上存在争论。基于细致的野外和室内沉积学研究，湖北兴山古洞口剖面中-上寒武统覃家庙群、三游洞群划分出8个岩相类型和3种沉积旋回类型，主要沉积于浅海碳酸盐岩台地潮下带和页岩盆地环境。采用沉积旋回叠置方式和Fischer图解方法，分析了上扬子区中-晚寒武世可容纳空间的变化历史，识别出18个四级旋回和7个三级旋回，并初步建立了高频海平面变化曲线。中-晚寒武世沉积相的时空间展布规律表明，扬子台地相对海平面逐渐降低，经历了从页岩盆地（或深潮下带）到浅潮下带环境的演变，沉积类型从较深水的陆源碎屑与碳酸盐的混合沉积变化为较浅水碳酸盐沉积。中、晚寒武世扬子台地碳酸盐岩沉积与全球性沉积特征表现一致，反映了该时期独特的全球“超暖期”气候和台地内部较高盐度的古海洋条件。

英文摘要：

The dolostone was extensively deposited in the Middle-Upper Cambrian of the Upper Yan- gtze Platform, South China. It was formed in particular palaeoclimatic and palaeooceanographical environ- ment, however, there still exist debates about its sedimentary environment and genesis. In this paper, based on the fine sedimentary research both in field and in laboratory, 8 lithofacies types and 3 sedimenta- ry cycles were identified, with the majority of the carbonates deposited in the subtidal zone or in the shaly basin of shallow marine carbonate platform, in the Middle-Upper Cambrian Qinjiamiao Group and Sanyou- dong Group at Gudongkou section in Xingshan, Hubei Province. By overlapping sedimentary cycles and computing Fischer plots, the history of accommodation change of the Upper Yangtze Platform during Mid- dle-Late Cambrian was analyzed, and 18 fourth-and 7 third-order cycles, which have preliminarily made up the curve of high-frequency relative sea-level change was identified. The temporal-spatial distribution of sedimentary facies in the Upper Yangtze Platform suggests that the relative sea-level of the platform was gradually dropping from Middle Cambrian to Late Cambrian, resulting in the sedimentary environment changing from shaly basin （or deep subtidal） to shallow subtidal, and the sedimentary facies changing from relatively-deep-water mixed deposition of terrigenous debris and carbonate sediments to relatively-shal- low-water carbonate deposition. The sedimentary characteristics in the Upper Yangtze Platform during Middle-Late Cambrian are consistent with the global change, indicating the unique global ＂super-green- house＂ palaeoclimate and internal-platform relatively-high-salinity palaeoceanography.

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