通过对东海陆架盆地西部地震和重磁资料的综合地球物理解释,对雁荡低凸起展布形态进行了细致刻画,凸起呈NE方向不连续展布于瓯江凹陷和闽江凹陷之间,长约170 km、宽约15-50 km.地震资料揭示雁荡低凸起上广泛发育了侏罗纪与白垩纪地层。厚度约为500-1500 m,展布面积约5000 km2,局部缺失中生界地层.凸起两侧中生代盆地结构差异明显,西侧瓯江凹陷为典型的断陷盆地,东断西超、断裂发育,半地堑、掀斜断块等中生界构造样式发育;东侧闽江凹陷为坳陷型盆地,断裂、火成岩不发育,挤压背斜、断背斜、反转构造等中生界构造样式发育.自由空间重力异常图与剩余重力异常图上,凸起表现为一系列NE向团块状重力高值区,而磁力异常△T、图上则表现为深部磁场强度低的特征,火成岩影响部位可见磁力高值异常.综合凸起及邻域重磁震、莫霍面深度等地质地球物理资料,认为雁荡低凸起为一元古界组成的古隆起,区别于东部的台北低凸起.同时,结合区域构造演化及沉积特征,推测侏罗纪时期雁荡低凸起与浙闽隆起区可能连为一体,晚白垩世近东西向伸展作用下浙闽隆起发生裂陷进而形成了雁荡低凸起.
Based on the geophysical interpretation of seismic,gravity and magnetic data of the western East China Sea Shelf Basin,this paper studied the distribution configuration of Yandang Low Uplift in detail and concluded that the uplift lied between Oujiang Sag and Minjiang Sag in a discontinuous NE-trending,about 170 km long and 15-50 km in width.There are widespread Jurassic and Cretaceous strata on the Yandang Low Uplift covering about 5000 km-2 except some absence locally and the strata thickness is about 500-1500 m.Oujiang Sag distinctly differs from Minjiang Sag in the Mesozoic basin structure.The former is a typical faulted basin with "boundary fault in the east and overlap in the west" and well-developed faults.It also has welldeveloped Mesozoic half-grabens,tilted fault blocks.However,Minjiang Sag is a down-warped basin with less faults and igneous rock.Mesozoic compressional anticlines,faulted anticlines and inverted structures occur in large amounts.The uplift appears as a series of high value areas in NE-trending on free air gravity anomalies map and residual gravity anomalies map,while it appears as low magnetic anomaly areas in deep part on the △T magnetic anomalies map and there are high values of magnetic anomalies where igneous rocks exist.These geophysical features suggest that Yandang Low Uplift is a Proterozoic uplift which is different from Taipei low uplift.Meanwhile,this paper presumes that Yandang Low Uplift and Zhe-Min uplift may be joined in a single entity in Jurassic and divided into two parts in late Cretaceous according to the regional tectonic evolution and sedimentary characteristics.