南海深海盆的沉积充填

Deposition in the South China Sea deep basin

依据大洋钻探井及地震剖面资料,定量确定南海同扩张期和后扩张期深海盆沉积充填差异及沉积物来源变化。研究显示,南海深海盆自渐新世(32 Ma)开始形成,随着南海二次扩张海盆范围逐渐扩大,海盆内主要充填火山碎屑角砾岩及火山灰,碳酸盐岩、超微化石软泥,泥质粘土、粉砂质粘土、泥岩及粉细砂岩。深海盆充填主要沉积物为晚中新世(11.6 Ma)以来的陆源碎屑沉积,丰富陆源碎屑的供给与南海闭合过程中同期区域构造事件(如青藏高原快速隆升、菲律宾板块俯冲)密切相关,也与晚中新世以来东亚季风增强以及源区强烈的风化剥蚀有关。

Based on the data obtained from ocean drilling wells and the seismic profile data,differences and changes in sediment sources of the deep-sea basin in the South China Sea(SCS)during syn-and post-seafloor spreading are determined quantitatively.It is shown that the oceanic basin of the SCS started to be formed as far back as the Oligocene(32Ma),and it extends with two spreading events of the SCS.The basin is mainly filled with volcanic conglomerate and ash,carbonate rock,ultra—microfossil mud,muddy clay,silty clay,mudstone and silt-fine grained sandstone.The main sediments in the deep-sea basins are terrigenous deposits since the Late Miocene(11.6Ma).The supply of plentiful terrigenous deposits is closely related to the regional tectonic events(such as the rapid uplift of the Qinghai-Tibet Plateau and the subduction of the Philippine plate)during the closing process of the SCS,as well as the strengthening of the East Asian monsoon since the Late Miocene and the strong weathering and erosion of the source area.