南海渐新世以来构造演化的沉积记录--ODP 1148站深海沉积物中的证据

南海ODP 1148站井深859 m、时间跨度32.8 Ma,是南海大洋钻探中取芯最长、年代最老的站位,详细记录了渐新世以来南海北部的演变历史。该站位深海沉积物地球化学分析结果显示,自早渐新世以来南海经历了复杂的沉积、构造演变过程。在32 Ma、30 Ma、28.5 Ma、25 Ma、23.5 Ma 和16 Ma以及10 Ma、8 Ma和3 Ma沉积物成分存在明显的突变或不连续面。特别是在晚渐新世沉积物成分发生剧烈改变,并伴有沉积间断和滑塌作用,代表着南海以及我国东部地区一次重大构造运动,该构造运动对我国近代地理格局的形成以及我国东部地区众多陆相盆地由断陷型转为坳陷型起到了极为关键的作用。

SEDIMENTARY RECORD OF THE TECTONIC EVOLUTION OF THE SOUTH CHINA SEA SINCE THE OLIGOCENE--Evidence from deep sea sediments of ODP Site 1148

ODP Leg 184 Site 1148 recovered up to 859 m deep-sea sediments spanning the fast 32.8 Ma from the northern South China Sea (SCS), which is the longest record known so far in recording the detail evolutionary history of the SCS since the Oligocene. Geochemical analysis reveal that the SCS has undergone complicated sedimentary and tectonic evolutionary processes. The composition of the sediments had obvious changes or discontinuities at 32 Ma, 30 Ma, 28.5 Ma, 25 Ma, 23.5 Ma, 16 Ma, 10 Ma, 8 Ma and 3 Ma, respectively, reflecting tectonic or environmental turning points. Especially, the great discontinuous change in the sediment composition at the Oligocene/Miocene boundary with slumps and sedimentation breaks indicates a period of important tectonic activities in the SCS and Eastern China areas. This tectonic event played a key role in the transforming of many sediments basins in the Eastern China from graben basins to down-warped basins, as well as in the formation of the general topographic character in the region.