北黄海盆地东部坳陷沉积层序充填与盆地演化

北黄海盆地位于苏鲁造山带—临津江造山带与胶—辽隆起之间。盆地划分为一凹二隆三坳共6个二级构造单元,其中东部坳陷钻遇中生界中侏罗统—下白垩统地层,以陆相沉积为主。划分为8个三级层序,中侏罗统发育2个三级层序,为拉张构造背景下的向上变细沉积序列;上侏罗统发育2个三级层序,沉积序列为拉张--构造反转背景下的向上变细序列。在上侏罗统沉积期末,挤压构造导致部分地层遭受剥蚀。下白垩统发育4个三级层序,受挤压构造控制,沉积地层剥蚀严重,局部缺少层序。钻井B32与B21的测井资料分析,认为Th/U比值可以有效对比,这种对比从古水深和海平面变化方面佐证了盆地的拉张--挤压构造的演化特征。构造演化史剖面分析,说明北黄海盆地东部坳陷的沉积层序发育和分布受构造活动性质的影响,同时也说明了盆地转换伸展构造背景的演化特征。

Filled characteristics of depositional sequence and evolution of eastern sag in North Yellow Sea Basin

The North Yellow Sea is located amongst the sulu orogenic belt，linjin river orogenic belt and jiao- liao uplift． The basin is divided into 6 secondary structure units which contain one depressed structure，two uplifts structure and three sags． Formations include middle Jurassic，upper Jurassic and lower cretaceous in the eastern depression． The sedimentary sequences were formed in continental environment． The basin filling succession can be classified into 8 third order sequences，and 2 of them are upward- fining sedimentary succession in extension tecton- ic background，in middle Jurassic． There are 2 third order sequences in upper Jurassic，which are upward- fining sedimentary succession in extension- inversion tectonic background． Compressional structure facilitated strata erosion in the late Jurassic． There are 4 third order sequences in lower cretaceous，controlled by compressional structure． The strata was eroded seriously and partial sequences missing． Logging data analysis of the Well B32 and Well B21 draw a conclusion that Th/U ratio of these 2 wells could be compared effectively，and the basin evolution of exten- sion structure -compressional structure were proved in terms of the paleo- water- depth and the sea level change． The structural evolution section analysis considered that the sequence development and distribution were affected by tec- tonic activity，and the basin evolution characteristics of transform structure- extensional structure were proved．