苏北盆地沉积环境演变及其构造背景

EVOLUTION OF THE SEDIMENTARY ENVIRONMENTS IN NORTH JIANGSU BASIN AND ITS TECTONIC SETTING

苏北盆地是晚中生代以后发育起来的大型沉积盆地,是中国东部含油气盆地之一。本文综合研究了苏北盆地沉积环境的演变特点,并从沉积作用与构造活动的关系以及古地磁和玄武岩等方面探讨了沉积环境变迁的大地构造背景。

The North Jiangsu Basin is one of the petroliferous basins in eastern China. As a large sedimentary basin with well-developed Meso-Cenozoic strata, it is the result of the combined action of tectonism and sedimentation.Sedimentation in the basin can be subivided into four stages corresponding to the tectonic cycles and the evolutional characters of the basin. Interior lacustrine and alluvial facies were most important under the arid tropical or subtropical climate in the Cretacous. The Palaeogene was a period with warm climate and the basin was subject to transgression in the earlier time and some relic lakes formed in the later. In the Neogene, climate became colder and the sediments of interior alluvial and lacustrine facies deposited in the vast depressed basin. The Quaternary was marked by the frequent climate variation and the cyclical transgression, which led to the alternations of continental and transitional or lintoral to shallow sea facies in the time and space distributions.The paleomagnetic study suggests that the left-handed horizontal displacement took place at the two sides of the Tancheng-Lujiang Fault Zone during the Early Creracous and the basement of the basin approximately reached the present location after that. Therefore the evolution of the sedimentary environments was restricted to a great extent by the Eurasian and the global environmental factors.The general trend of the environmental evolution of the basin may be summarized as that the 'continentility' of tectonic environment strengthened and that of sedimentary environment weakened.