台湾岛以东海域海底地形特征及其构造控制

基于2000年5~6月在台湾岛以东海域调查获得的多波束全覆盖测深等地质和地球物理资料,对该海域海底地形特征进行了研究,探讨了构造对海底地形的控制作用及其构造地质意义.研究表明,琉球岛弧岛坡区和琉球海沟表现为典型的西太平洋沟-弧-盆体系控制下的构造地形;台湾岛东部岛坡等深线近南北向平行密集排列,地形坡度大,弧陆碰撞造就了该区独特的地形特征;花东盆地海底峡谷发育,其形成主要受基底起伏和走滑断裂的控制;加瓜海脊东西两侧水深和地形特征明显不同,但其基底可能属于花东盆地,加瓜海脊的东侧对应了两个不同性质板块的边界;西菲律宾海盆表现为北西向线状脊-槽相间排列,并遭受北东向转换断层的切割,根据海底地形、转换断层和磁异常条带的方向推测,研究区海底形成于距今60~45Ma的西菲律宾海盆北东-南西向扩张期.

The topographical characteristics in the area off eastern Taiwan Island and their tectonic implication

On the basis of bathymetric data and other geological and geophysical data obtained during first survey in the area off eastern Taiwan Island from May to June in 2000,the topogr aphical features of the region,the tectonic control to the seafloor topography and their tectonic implication were studied and discussed.The results have revealed that both the slope zone of the Ryūkyū arc and the Ryūkyū Trench presenta typical morphot ectonic characteristics controlled by the trench-arc system in the West Pacific Ocean.At the slope of eastern Taiwan Island the isobathic lines parallel the coast line and distribute densely in nearly N-S direction and the slope gradient of topog raphy is large.Such a unique feature is at tributed to the collision of the Luzon arc and Eurasia continent.In the Huadong(Huatung) Basin,turbidity fans and submarine canyons are well developed,its form ations are mainly related to the steep topo graphy of the slope of the Luzon arc and the abundant supply of sediments.These submarine canyons are controlled by basement highs and strike-slip faults.On the eastern side and western side of the Gagua Ridge,both the water depth and morpho logical features are different,but the basement of Gagua Ridge belongs to the Huadong Basin.The eastern side of the Gagua Ridge(123°12'E) corresponds to the boundary of two plates with different ages.In the West Philippine Basin,linear ridges and troughs in a N W trending are identified,which are dissected by a N-E trending transform fault.According to the seafloor topography features,the direction of the transform fault and the magnetic anomaly lineations,the seaflo or of this region was formed during 60~45 Ma B.P.when the West Philippine Basin was spreading along NE-SW relative to present orientation.