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Based on the drilling data,the geological characteristics of the coast in South China,and the interpretation of the long seismic profiles covering the Pearl River Mouth Basin and southeastern Hainan Basin,the basin basement in the northern South China Sea is divided into four structural layers,namely,Pre-Sinian crystalline basement,Sinian-lower Paleozoic,upper Paleozoic,and Mesozoic structural layers.This paper discusses the distribution range and law and reveals the tectonic attribute of each structural layer.The Pre-Sinian crystalline basement is distributed in the northern South China Sea,which is linked to the Pre-Sinian crystalline basement of the Cathaysian Block and together they constitute a larger-scale continental block—the Cathaysian-northern South China Sea continental block.The Sinian-lower Paleozoic structural layer is distributed in the northern South China Sea,which is the natural extension of the Caledonian fold belt in South China to the sea area.The sediments are derived from southern East China Sea-Taiwan,Zhongsha-Xisha islands and Yunkai ancient uplifts,and some small basement uplifts.The Caledonian fold belt in the northern South China Sea is linked with that in South China and they constitute the wider fold belt.The upper Paleozoic structural layer is unevenly distributed in the northern South China.In the basement of Beibu Gulf Basin and southwestern Taiwan Basin,the structural layer is composed of the stable epicontinental sea deposit.The distribution areas in the Pearl River Mouth Basin and the southeastern Hainan Basin belong to ancient uplifts in the late Paleozoic,lacking the upper Paleozoic structural layers.The stratigraphic distribution and sedimentary environment in Middle-Late Jurassic to Cretaceous are characteristic of differentiation in the east and the west.The marine,paralic deposit is well developed in the basin basement of southwestern Taiwan but the volcanic activity is not obvious.The marine and paralic facies deposit is distributed in the eastern Pearl River Mouth Basin basement and the volcanic activity is stronger.The continental facies volcano-sediment in the Early Cretaceous is distributed in the basement of the western Pearl River Mouth Basin and Southeastern Hainan Basin.The Upper Cretaceous red continental facies clastic rocks are distributed in the Beibu Gulf Basin and Yinggehai Basin.The NE direction granitic volcanic-intrusive complex,volcano-sedimentary basin,fold and fault in Mesozoic basement have the similar temporal and spatial distribution,geological feature,and tectonic attribute with the coastal land in South China,and they belong to the same magma-deposition-tectonic system,which demonstrates that the late Mesozoic structural layer was formed in the background of active continental margin.Based on the analysis of basement structure and the study on tectonic attribute,the paleogeographic map of the basin basement in different periods in the northern South China Sea is compiled.
Based on the drilling data, the geological characteristics of the coast in South China, and the interpretation of the long seismic profiles covering the Pearl River Mouth Basin and southeastern Hainan Basin, the basin basement in the northern South China Sea is divided into four structural layers , namely, Pre-Sinian crystalline basement, Sinian-lower Paleozoic, upper Paleozoic, and Mesozoic structural layers. This paper discusses the distribution range and law and reveals the tectonic attribute of each structural layer. The Pre-Sinian crystalline basement is distributed in the northern South China Sea, which is linked to the Pre-Sinian crystalline basement of the Cathaysian Block and together they constitute a larger-scale continental block-the Cathaysian-northern South China Sea continental block. The Sinian-lower Paleozoic structural layer is distributed in the northern South China Sea, which is the natural extension of the Caledonian fold belt in South China to the sea area. The sediments are d erived from southern East China Sea-Taiwan, Zhongsha-Xisha islands and Yunkai ancient uplifts, and some small basement uplifts. Some Caledonian fold belt in the northern South China Sea is linked with that in South China and they constitute the wider fold belt. upper Paleozoic structural layer is unevenly distributed in the northern South China. In the basement of Beibu Gulf Basin and southwestern Taiwan Basin, the structural layer is composed of the stable epicontinental sea deposit. The distribution areas in the Pearl River Mouth Basin and the southeastern Hainan Basin belong to ancient uplifts in the late Paleozoic, lacking the upper Paleozoic structural layers. Stratigraphic distribution and sedimentary environment in Middle-Late Jurassic to Cretaceous are characteristic of differentiation in the east and the west. The marine, paralic deposit is well developed in the basin basement of southwestern Taiwan but the volcanic activity is not obvious. The marine and paralic facies deposit is distributed in the eastern Pearl River Mouth Basin basement and the volcanic activity is stronger. continental facies volcano-sediment in the Early Cretaceous is distributed in the basement of the western Pearl River Mouth Basin and Southeastern Hainan Basin. Upper Cretaceous red continental facies clastic rocks are distributed in the Beibu Gulf Basin and Yinggehai Basin. NE direction granitic volcanic-intrusive complex, volcano-sedimentary basin, fold and fault in Mesozoic basement have the similar temporal and spatial distribution, geological feature, and tectonic attribute with the coastal land in South China, and they belong to the same magma-deposition-tectonic system, which demonstrates that the late Mesozoic structural layer was formed in the background of active continental margin. Based on the analysis of basement structure and the study on tectonic attribute, the paleogeographic map of the basin basement in different periods in the northern South China Sea is compiled.