南海浊流地貌

Turbidity current related landforms in the South China Sea

南海深海底部浊流地貌十分发育。陆坡区有大量的海底峡谷,部分峡谷的谷底、越岸区或出口部位分布有超临界流成因的大型沉积物波和周期阶坎底形。多数峡谷在陆坡脚的出口处并未形成像样的海底扇,而深海平原中却保有高丰度的浊流沉积。这可能暗示,南海峡谷浊流的能量较高,即使在经历陆坡脚的减速之后仍有足够的能量维持其沿平缓的深海平原作较长距离的搬运。浊流地貌的出现大多始于晚中新世,其成因与南海及周缘强烈的构造活动有关。

Submarine landforms associated with turbidity currents are well developed in the South China Sea(SCS). There are numerous submarine canyons in the continental slopes. Sediment waves and cyclic step bedforms related to the supercritical turbidity currents are distributed along the thalwegs, on the overbank areas or off the outlets of some submarine canyons.However, large-scale submarine fans at the foot of the continental slopes are rarely observed;on the other hand, a high proportion of turbidites are found being preserved in the pelagic to the hemipelagic succession of the abyssal plain. We suggest that the turbidity currents traversing the submarine canyons could be of high energy, enough to sustain a longer distance transport along the abyssal plain even after the deceleration at the foot of the continental slopes. The turbidity-current associated landforms in the SCS were mostly initiated in the late Miocene, and might be closely related to the active plate tectonics in the SCS and surrounding areas.