台湾地区弧-陆碰撞控制的海相前陆盆地

Marine foreland basin in the process of arc-continental collision in Taiwan Region

依据现有的地震、钻井和野外地质资料,综合前人关于台湾地区板块相互作用、区域大地构造、岩浆活动、弧-陆碰撞过程、沉积盆地、层序地层等方面的研究成果,本文比较系统地论述了台湾地区弧-陆碰撞过程中的盆地特征及演化规律,认为约15 Ma以吕宋岛弧带为主的弧-陆碰撞对盆地样式和盆地演化产生了重大影响,自东向西,分别形成海沟、沟-坡盆地、弧前盆地、弧内盆地和弧后海相前陆盆地。弧后海相前陆盆地为台湾碰撞带最大的沉积体系,是前陆盆地发育的早期阶段,之前还经历了陆缘断陷盆地阶段和被动大陆边缘盆地阶段。研究区沉积物从源到汇的搬运过程中,盆地的沉积与构造之间的时间存在明显滞后。9~6 Ma期间,吕宋岛弧形成;晚上新世(3 Ma),台湾海相前陆盆地的沉积环境、沉积相、物源等才发生显著变化,沉积物源方向由被动大陆边缘盆地期的向SE倒转为向SW,盆地沉积与构造运动之间滞后时间长达3~6 Ma,远大于一般认为的0.1~1 Ma。沉积物沿年轻造山带走向搬运、基底沉降导致近物源区粗碎屑物质的沉积、整个搬运体系中沉积物的局部保存与释放等因素可能是导致时间滞后的主要原因。

Based on seismic,drilling and field geological data and combined with the recent results on the plate interaction,regional tectonics,magmatic activity,arc-continental collisional processes,sedimentary characteristics and sequence stratigraphy for the Taiwan and adjacent area,this paper systematically discusses the marine foreland basin and its evolutionary history and the process of arc-continental collision in the Taiwan Region.The arc-continent collision between the Luzon Island Arc and the Eurasian passive continental margin at-15 Ma has significant impact on the types and evolution of the basin systems.From the east to the west,the trench,trench-slope basin,fore-arc basin,intra-arc basin and retro-arc foreland basin developed during the arccontinent collision.The marine retro-arc foreland basin which is an early stage of the foreland basin is the largest sedimentary system of the Taiwan collision zone.The study area also underwent the marginal faulted basin and passive continental margin basin stage before the marine retro-arc foreland basin has taken shape.In the process of sediment transportation from the source to trap,the time of sedimentary filling shows clear hysteresis behind the tectonic stage.The Luzon Arc formed during 9-6 Ma,while the sedimentary environment,sedimentary facies and provenance in the Taiwan Marine Foreland Basin began to change until the late Pliocene（3 Ma）;the source direction switched from SE of the passive continental margin basin stage to SW of the foreland basin stage.The time lagged for 3-6Ma between the sedimentary filling stage and the tectonic stage,which is far longer than that of the generally believed 0.1-1Ma.These factors,such as the transportation of sediments along the young orogenic belt,the sedimentation of coarse debris near the provenance caused by basement subsidence,and the local preservation and release of sediments in the whole transportation system,may give rise to the hysteresis of the sedimentary filling stage behind the tectonic stage.