南海东北部台湾浅滩陆坡的浊流沉积物波的发育及其成因的构造控制

Development and Its Tectonic Activity's Origin of Turbidity Current Sediment Wave in Manila Trench,the South China Sea

南海东北部马尼拉海沟发育有面积达35000km2的、壮观的沉积物波波域,水深2600～4100m。基于波域的特征、区域分布、物质组成等,判断其为重力流成因。该波域于1.2Ma开始起动,从而形成了和下伏平行反射截然不同的波状反射,二者之间为沉积物波的起动面。该波域的发育史受控于台湾造山运动的发育史,吕宋岛弧在北西西向运动的菲律宾海板块的携带下,于6.5Ma左右和欧亚大陆边缘发生斜向弧—陆碰撞,碰撞焦点持续向南转移,于1.2Ma左右转移至台湾南部,造成台湾南部的物理剥蚀、乃至向毗邻深水的碎屑供应急剧增加,改变了深水沉积动力学状态,浊流活动的强度和频率极大加强,从而开始了该波域的起动和发育。该沉积物波的发育和台湾造山运动构成了完美的构造活动和沉积响应关系。

A spectacular sediment wave field which situated at water depth of 2 600 - 4 100m cover area of approxi- mately 35 000 km^2 in Manila Trench, the northeast South China Sea. The sediment field can be judged the turbidity current＇ s origin based on its related characters, regional distribution and material composition, which initiated at 1.2 Ma and build the sediment body exhibiting the wave seismic reflection and thus is different from the underlying parallel seismic reflection distinctly. A surface of initiation can be distinguished between the two different sediment bodies. The development of the sediment wave is totally controlled by the characteristic development of Taiwan Orogenesis. Luzon Arc be part of the Philippine Sea Plate which move towards NWW direction collide with Eurasian Continent Margin at approximately 6.5 Ma obliquely and the focus of collision propagated southward consistently because of the inherent oblique collision. In 1.2 Ma the focus of collision arrived at the present south part of Taiwan Island and so significantly enhanced the physical denudation rate of related region, thus the rapidly increased the supply of material to deepwater environment, and result in quite enhancement of the strength and the frequency of turbidity current, and resuhantly significantly modified the sediment dynamics status of deepwater environment. Just under such setting the development of sediment wave can be initiated and developed. The Taiwan Orogenesis and development of sediment wave constitute a perfect pair of tectonic activity and response of sedimentation.