东海陆架南部邻近陆域晚三叠世—早侏罗世沉积古环境分析

Paleo-environment of the Late Triassic-Early Jurassic in the land area next to the southern East China Sea Shelf

  • 摘要: 东海陆架盆地南部邻近陆域主要包括福建东南部以及广东东北部的广大地区。结合野外地质考察、岩石薄片镜鉴及样品地球化学测试结果等资料,研究了该地区晚三叠世—早侏罗世沉积古环境。研究区晚三叠世—早侏罗世时期,属于温湿气候环境,南部的粤东地区沉积水体深度较大,因此,大部分样品指示厌氧环境。晚三叠世时,整个东海陆架南部邻近陆域自南向北水体逐渐变浅,南部主要为滨海—浅海陆棚—深水陆棚环境,北部主要表现为受海侵作用影响的海陆过渡相环境;早侏罗世时,南部主要表现为水体较深的深水陆棚环境,北部主要表现为海陆过渡相—陆相沉积环境。通过对具有相同大地构造背景的邻近陆域沉积古环境的研究,从而可以推断缺乏钻井资料的东海陆架盆地南部沉积古环境自北向南由陆及海,为后续开展海域中生界油气地质条件研究提供依据。

     

    Abstract: The research area, the land next to the southern East China Sea Shelf Basin, includes both the southeastern part of Fujian Province and the northeastern part of Guangdong Province. Based on field geological survey, microscopic observation and geochemical testing, the paleo-environment of the Late Triassic-Early Jurassic deposits of the area is carefully investigated. It is revealed that the sediments are deposited in a deep water anaerobic environment during late Triassic-Early Jurassic, when the region was dominated by warm and humid climate in the southeastern part of Guangdong Province. During Late Triassic, the southern part of the land area gradually became shallower northwards. Consequently, the southern part of the study area was dominated by a assemblage of coast, shallow shelf and deep shelf, while the northern part dominated by a marine-land transitional environment under the affect of transgression. In early Jurassic, the southern part of the region became an outer shelf with great water depth, and the northern part become marine-continental transitional and sometimes continental environment alone. Based on the paleo-environment research of the adjacent land area with the same geotectonic background, it is concluded that the Mesozoic paleo-environment varied southwards from continent to marine in the southern part of the East China Sea Shelf Basin. The paleo-geographic pattern is helpful to study the Mesozoic petroleum geology in the region.

     

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