【作者】 傅命佐；

【导师】 王永吉；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋地质学， 2005， 博士

【摘要】 冲绳海槽是当今世界上唯一的在大陆边缘张裂形成的、处于早期演化阶段的活动性大陆边缘弧后盆地。本文利用多波束勘测数据等精密地形资料和地质地球物理调查资料与前人研究成果,通过对冲绳海槽及其邻域的地质构造、新生代地层、地球物理场特征的对比分析、构造地貌分类与制图研究等方法,对冲绳海槽的地壳性质、地质构造、地层结构、构造地貌特征和分布格局、形成机制、时代、演化历史等进行了深入的研究,编绘了 1:500 000 冲绳海槽构造地貌图,建立了冲绳海槽构造地貌发育模式。指出: (1)冲绳海槽的构造地貌发育、演化和分布格局,主要受菲律宾海板块与欧亚大陆板块俯冲、碰撞作用(琉球海沟俯冲带和台湾-吕宋岛弧碰撞带)所产生的构造、岩浆活动的控制。 (2)冲绳海槽的构造地貌格局受两组构造线的控制,形成平行于俯冲带构造线的构造地貌带和垂直于俯冲带构造线的构造地貌带,简称“东西分带、南北分块”的构造地貌格局。平行于俯冲带构造线的构造地貌带是弧后拉张应力场作用下形成的以雁行式裂谷轴为中心的 ENE-NE-NNE 向构造地貌分带,垂直于俯冲带构造线的地貌分块的形成原因,一方面是菲律宾海板块相对欧亚大陆板块运动速度和板块运动方向与俯冲带走向之交角的变化所导致的冲绳海槽地壳厚度和地壳性质的变化,另一方面是菲律宾海板块所驮载的大洋海岭、洋底高原等对仰冲板块的差异顶托作用。冲绳海槽的北、中、南构造地貌分块以 27°45′-28°02′N 和26°25′-26°35′N 的槽底斜坡带为界。 (3)冲绳海槽的形成、演化经历了三次大的构造运动,分别称为冲绳海槽运动一幕、二幕、三幕。每次构造运动都与菲律宾海板块相对欧亚大陆板块运动方向、方式的改变相关。晚中新世-上新世初的冲绳海槽运动一幕使东亚大陆边缘的“古岛弧”褶皱隆起,在褶皱轴部形成张裂地堑,形成冲绳海槽的雏形,琉球弧地块从东亚大陆裂离;上新世末-更新世初的冲绳海槽运动二幕以大规模正断层活动和岩浆活动为特征,使早期形成的冲绳海槽北、中、南段的地堑贯通,形成统一的冲绳海槽盆地,并向西南扩展;在海槽盆地的中部形成雁行式排列的中央裂谷轴地堑带,冲绳海槽的构造地貌格局基本形成;晚更新世-全新世的冲绳海槽运动三幕以正断层活动为主。 (4)目前,北冲绳海槽仍处于裂谷拉张演化阶段,中冲绳海槽处于裂谷拉张与海底扩张的转换阶段,南冲绳海槽已发生海底扩张,地堑中心已有新生洋壳生成。 (5)冲绳海槽在构造地貌上构成东海陆架和琉球岛弧的天然分界。更多还原

【Abstract】 The Okinawa Trough (OT) is the solitary active backarc basin in the world that is formed by extensional rifting in the continental marginal zone and is in the early stage of evolution. Contrast analyses of geological structures, Cenozoic stratigraphy and geophysical fields between the OT and its surrounding areas (i.e., the East China Sea shelf, the southern Japan Arc, the Ryukyu trench-arc system, the Philippine Sea basin and the Taiwan-Luzon collision zone) are conducted. The tectonic geomorphological types are classified based on the theory of plate tectonics. And a tectonic geomorphological map of the OT and its surrounding areas is compiled. Based on these, the crustal properties, geological structures and stratigraphic patterns of the OT are examined in details; the tectonic geomorphological characteristics and distribution patterns of the OT are delineated, the morphogenic mechanism, geomorphologic ages and evolutionary history of the OT are determined, and the evolutional model of the tectonic geomorphology of the OT is established. The following remarks are concluded. (1) The formation, evolution and distribution patterns of the tectonic geomorphologic features of the OT are controlled by the tectonic movements and magmatic activities caused by the subduction and collision between the Philippine Sea plate (PH) and the Eurasia plate (EA). (2) The tectonic geomorphologic patterns of the OT is controlled by two sets of structural lines parallel and perpendicular to the Ryukyu trench subduction zone respectively, forming the geomorphologic zonation parallel to, and the geomorphologic blocking perpendicular to the subduction zone, called E-W zonation and N-S blocking respectively. The E-W geomorphologic zonation parallel to the subduction zone is formed under the extensional stress field in the backarc zone of the Ryukyu trench-arc-backarc system, consisting of a series of geomorphologic zones extending in the direction parallel to the trending of the OT, with a series of en echelon rifting depressions as the central zone. The N-S geomorphological blocking perpendicular to the structural line of the subduction zone is due to the different thicknesses and properties of the crusts in the northern, central and southern OTs, which are related to the different velocities of the relative movement between the PH and the EA, the different intersection angles between the PH movement direction and the trending of the subduction zone, and owing to the upward butting of the ridges and plateaus on the subducting PH to the overriding plate. In term of tectonic geomorphology, the northern, central and southern OTs are divided by the two great clinoforms located at 27°45′-28°02′N and 26°25′-26°35′N, respectively. (3) The formation and evolution of the OT have experienced three major tectonic movements, called the first, second and third phases of the OT movements respectively. Each of the phases is related to the changes of the direction and/or mode of the relative movements between the PH and the EA. The first phase of the OT movement occurred from the late Miocene to the early Pliocene, which caused the former island arc at the margin of the east Asia mainland folded and upwarped. A series of rifting grabens formed along the axial zone of the upwarped fold, which are the embryonic forms of the OT. As a result, the Ryukyu land mass was separated apart from the east Asia mainland by the original OT. The second phase of the OT movement occurred from the end of the Pliocene to early Pleistocene, which is characterized by large-scale normal faulting and magmatisms. This phase of the OT movement caused the original grabens formed during the first phase to link up as a united trough basin and extend southwestwards to northern Taiwan Island. A series of en echelon rifting grabens were formed along the axis of the trough. The major tectonic geomorphologic pattern of the OT was established. The third phase of the OT movement happened from late Pleistocene to Holocene, which is characterized mainly by less-scale normal faul更多还原