Discussion on the spatial and temporal difference of Cenozoic rift formation and evolution and its genesis mechanism in the Pearl River Estuary Basin
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摘要: 【目的】为加深对珠江口盆地内不同构造单元之间裂陷形成和演化的时空差异性的认识。【方法】本文基于二维地震剖面资料,通过构造解析、平衡剖面恢复和断裂活动速率计算等方法,分析了珠江口盆地先存构造、基底岩性、断裂体系及构造演化的时空差异性,并结合岩浆活动和动力学背景,探究了珠江口盆地内坳陷构造差异的成因。【结论】取得如下认识:珠江口盆地基底先存构造主要发育了一系列NE向逆冲断裂和与之共轭的NW向先存逆冲断裂体系;盆内断裂发育自西向东以NE、NEE、近EW和NWW走向为主,控制着盆地裂陷期的构造格局;裂陷期部分断裂沿基底先存断裂长期继承发育,部分断裂由于基底先存构造及岩性的差异具有不同的抗张和抗剪强度,同时受控于周缘板块运动、岩浆作用和区域应力场变化等,发生由NE-NEE向伸展性质顺时针转变为近EW-NW向伸展-走滑主导的变化过程;在裂后期间断裂活动减弱,但在盆地中部近EW向和NW向断裂较为活动,盆地裂陷结构由北向南发生“下厚上薄”狭长型窄地堑、半地堑向“上厚下薄”宽缓型地堑、半地堑转变,盆地沉积中心展布呈现沿NE向迁移的规律。Abstract: To deepen the understanding of the temporal and spatial differences. In the this study is based on the seismic profile data of the the Pearl River Mouth Basin, using the methods of structural analysis, balanced profilerestoration and fault activity rate calculation, the fault system and structural evolution process of the the Pearl River Mouth Basin are analyzed. Moreover, the. causes of structural differences in the depressions in this Basin are explored in combination with the pre-existing structure, basement characteristics and dynamic background of the basin. The main results are as follows: The basement pre-existing structures in the Pearl River Mouth Basin mainly developed a series of NE trending thrust faults and the conjugate NW trending pre-existing thrust fault system; The faults in the Pearl River Mouth Basin show NE, NEE, near EW and NWW strike from west to east, controlling the tectonic framework of the basin during the rifting period; The evolution stages of the basin are divided into four stages: the early stage of rift (E1sh-E2w), the development stage of rift (E3e), the depression stage (E3z-N1z-N1h), and the tectonic activation stage (N1y-N2w-Q); The fault system in the basin mainly exhibits a clockwise transition from NE-NEE extensional properties to nearly EW-NW extensional strike slip properties. This is due to the long-term inheritance and development of some main faults along the basement pre-existing faults during the rift period. At the same time, the differences in basement pre-existing structures and lithology result in different tensile and shear strengths, as well as being controlled by peripheral plate movement, magmatism, and regional stress field changes. The rift structure of the basin has undergone a transformation from north to south, from narrow and narrow grabens and semi grabens with "thick below and thin above" characteristics to wide and gentle grabens and semi grabens with "thick above and thin below" characteristics. The distribution of sedimentary centers in the basin shows a migration pattern along the NE direction.
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