东海陆架盆地中新生代构造演化对烃源岩分布的控制作用

东海陆架盆地为发育于克拉通基底之上的中、新生代叠合盆地,该盆地经历了晚三叠世(?)—中侏罗世克拉通边缘坳陷盆地、白垩纪弧前盆地和晚白垩世末—新生代弧后裂陷盆地等3个构造演化阶段。侏罗纪盆地和白垩纪盆地主要残留在中央隆起带;新生代盆地演化在平面上表现出裂陷由西向东迁移的特征。不同时代盆地构造类型和大地构造位置控制了盆地烃源岩发育层位及平面分布:西部坳陷带以古新统月桂峰组湖相泥岩和灵峰组、明月峰组滨海相煤系地层为主要烃源岩;中央隆起带以上三叠统—中侏罗统福州组为主要烃源岩;东部坳陷带以始新统平湖组煤系地层为主要烃源岩,渐新统和中新统煤系地层为次要烃源岩。西湖凹陷天台斜坡带为中、新生代有利烃源岩的叠合区,具有“中生中储”和“新生中储”的优势,是东海陆架盆地天然气勘探的有利地区。

Controls of Mesozoic and Cenozoic tectonic evolution on source rock distribution in East China Sea shelf basin

As a Mesozoic and Cenozoic superposed basin on a cratonic basement,East China Sea shelf basin has three periods of tectonic evolution:Late Triassic(?)-Middle Jurassic depression on a cratonic margin,Cretaceous forearc basin and Latest Cretaceous-Cenozoic backarc basin.Currently,the Jurassic and Cretaceous basins are mainly resides in the central uplift belt,and the Cenozoic basin evolution exhibits an eastward migration of rifting horizontally.The development and horizontal distribution of source rock are controlled by tectonic types and locations in various periods in the basin.For the western depression belt,lacustrine mustone in Paleocene Yueguifeng Formation and littoral coal measures in Lingfeng and Mingyuefeng Formations constitute main source rocks.In the central uplift belt,Upper Triassic-Middle Jurassic Fuzhou Formation provides major source rocks.There are a major source rock in coal measures of Eocene Pinghu Formation and a minor source rock in Oligocene and Miocene coal measures in the eastern depression belt.As a superposition area of favourable source rocks,Tiantai slope in Xihu sag is characterized by advantages of "Mesozoic source and Mesozoic reservoir" and "Cenozoic source and Mesozoic reservoir",forming a sweet area for gas exploration in East China Sea shelf basin.