Shiyou shiyan dizhi (Sep 2020)
Paleozoic basin prototype evolution and source rock development in the South Yellow Sea
Abstract
Drill samples and outcrops confirmed that three sets of source rocks developed in the Lower Yangtze Block area, namely, the Lower Cambrian Mufushan Formation, the Upper Ordovician Wufeng Formation-the Lower Silurian Gaojiabian Formation, and the Permian. This tectonic environment determined the evolution of the basin, which then affected the distribution of lithofacies and source rocks. During the deposition of the Lower Cambrian Mufushan Formation, the South Yellow Sea Basin was a passive continental cratonic margin basin undergoing regional extension. The basin facies and deep-water shelf facies developed around the paleo-uplift or platform, which were the dominant facies for the development of source rocks. It was predicted that this set of source rock developed well in the Middle Uplift and the northern part of the South Yellow Sea Basin. During the depositing of Wufeng and Gaojiabian formations, the South Yellow Sea Basin was a compressional foreland basin. The basin facies, slope facies and deep-water shelf facies were distributed in strips from the northwest to the southeast of Lower Yangtze area. The basin facies and deep-water shelf facies were dominant facies in which source rocks developed well. It was predicted that the source rocks of Wufeng-Gaojiabian formations were distributed mainly in the middle and north part of the South Yellow Sea Basin. During the deposition of the Upper Permian Longtan Formation, the South Yellow Sea Basin experienced active continental margin convergence. The sedimentary facies in the basin were scattered in ring belts. Delta and tidal flat facies were dominant with moderate to good quality source rocks. It was predicted that the source rocks of the Longtan Formation developed in the middle part of the South Yellow Sea Basin, which was the secondary source rock of Paleozoic in the South Yellow Sea Basin.
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