中国早震旦世构造-岩相古地理

Tectono-lithofacies-palaeogeography of China in the Early Sinian

早震旦世是中国各主要板块普遍发育海相沉积的开始,是目前被证实是最早的有效海相烃源岩的发育时期。该时期是中国各主要陆块处于新一轮洋盆扩张、板块离散、海水进侵旋回的初始期,总体的构造-沉积格局呈"多岛洋"。陆块的固结年龄、规模和稳定性在很大程度上控制着三大准地台及其周边的古地理面貌和岩相组合。华北准地台的基底固结年龄最早,规模最大,稳定性最好,因此在早震旦世以大面积古陆为主,在台地边缘以浅海滨岸相碎屑岩为主,浅水碳酸盐台地相和深水斜坡相不发育。塔里木准地台在早震旦世以海陆并存为特征,在塔北、塔中存在古陆剥蚀区,向外以浅海滨岸相碎屑岩和斜坡-盆地相混合沉积为特色。扬子准地台在康滇地区存在古陆,其余地区基本为海水所侵没,发育台地-斜坡-盆地的完整相序。这种构造-沉积格局具有长期的继承性影响,主要表现在:(1)在早古生代早期的洋盆扩张-海侵旋回,扬子和塔里木比华北更发育被动陆缘斜坡-盆地相烃源岩;(2)在早古生代晚期的洋盆关闭-海退旋回,华北最先经历海退,而扬子和塔里木仍在一定时间内保持海相沉积,甚至在准地台内部发育较深水烃源岩相。

In the early Sinian, marine sediments began to prevail on all main plates of China, and the earliest effective marine hydrocarbon source rocks began to develop; it is the time of the beginning of a new cycle of ocean spreading, plate disperse and marine transgression, and the main plates of China had an overall tectono- sedimentary framework of archipelagic ocean. The concretion age, scale and stability of blocks controlled the lithofacies-palaeogeographical characteristics of the three main paraplatforms and their peripheral areas to a great extent. The North China paraplatform had the earliest concretion ages the largest scale and the highest stability, so during the early Sinian, a large area of old land was developed with clastie rocks of shoreland facies on the edge of the platform, while both shallow carbonate platform facies and deep slope facies were not developed. The Tarim paraplatform was characterized by coexistence of continental and marine facies, and there were two eroded old land areas： the North Tarim and the Middle Tarim, from which outwards it is characterized by epicontinental onshore facies clastie rocks and mixed sediments of clinothem with basin facies developed successively around the two old land eroded areas. The Yangtze paraplatform was almost all submerged and developed a complete facies sequence from platform, clinothem to basin deposits, except that old land existed in the Kang-Dian（ i. e. , Xikang-Yunnan） area. The tectono-sedimentary framework had long- term inheritant effects, which manifested in two main aspects： （1） during the cycle of ocean spreading and marine transgression from the early Sinian to the early period of the Early Paleozoic, the Yangtze paraplatform and Tarim paraplatform were more tended to develop marine hydrocarbon source rocks of passive continental margin clinothem-basin facies than the North China parapiatform; （2） during the cycle of ocean closing and marine regression in the late period of the Early Paleozoic, the North China paraplatform was subjected to the marine regression earlier, the Yangtze paraplatform and Tarim paraplatform retained marine sedimentary environmem during a relatively long period, and, moreover, hydrocarbon source rocks of deep water depression facies were developed better in these two paraplatforms than in the North China paraplatform.