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    四川九寨沟地区泥盆—三叠系多重地层划分对比及沉积环境

    Multiple stratigraphic classification and correlation of the Devonian-Triassic in the Jiuzhaigou area, Sichuan, and its sedimentary environment

    • 摘要: 提要:位于青藏高原东缘四川盆地接壤处的四川九寨沟地区发育了总厚6 000 m以上的碳酸盐岩,通过1∶5万区域地质调查和一系列专项调查,将该区内岩石地层划分为9个岩组。生物地层划分了3个珊瑚组合带,3个腕足组合带,1个腕足顶峰带, 2个双壳顶峰带以及有孔虫组合带和顶峰带各1个。生态地层研究划分了两个生态群落。根据地球化学元素特征划分了11个地球化学段。研究了地层的常量元素和碳同位素特征。对碳酸盐岩进行了微相分析。综合各项沉积标志进行了沉积环境判别,其中岷河组沉积环境最为特殊,属于碳酸盐岩和陆源碎屑的混合沉积体系。

       

      Abstract: Abstract:A sequence of carbonate rocks with a total thickness of over 6000 m is developed in Jiuzhaigou in the border region between the eastern margin of the Qinghai-Tibet Plateau and Sichuan basin. Based on the 1∶50000 regional geological survey and a series of special-subject surveys in this areas, nine formation-complexes are recognized in the lithostratigraphic context, and 3 coral assemblage-zones, 3 assemblage-zones and 1 acme-zone of brachiopods, 2 bivalve acme-zones and 1 assemblage-zones and 1 acme-zone of foraminifers are distinguished in the biostratigraphic context. In terms of ecostratigraphy, 2 communities are established. According to the characteristics of geochemical elements, 11 geochemical intervals are identified. In addition, the authors have studied the major element and carbon isotopic features and conducted microfacies analysis of carbonate rocks. Through integrating various sedimentary indicators, the authors have made discrimination of sedimentary environments, of which the sedimentary environment of the Minhe Formation is unique, belonging to a mixed carbonate and terrestrial clastic sedimentary system.

       

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