南海西北部莺歌海盆地陆架晚更新世三角洲及其控制因素

Late Pleistocene delta and its controlling factors on the shelf of Yinggehai Basin in the northwestern South China Sea

莺歌海盆地陆架区作为南海北部的一个重要地质构造单元,记录了第四纪以来沉积和海平面变化的丰富信息。通过对研究区高分辨率单道地震剖面的解释,结合深水区钻孔资料,分析了该地区晚第四纪地层的沉积特征,研究区浅部地层划分出层A和层B 2套地层单元,并进一步对研究区三角洲平原、三角洲前缘和前三角洲3种沉积亚相的地震特征进行了解释分析。钻孔AMS^(14)C与光释光测年结果表明,三角洲形成于晚更新世65~56 ka,即MIS4晚期-MIS3早期。结合钻孔岩性和有孔虫分布特征以及区域地质、沉积背景等资料,开展了三角洲形成的控制因素分析,认为莺歌海盆地的构造和古地貌、海南岛隆升、物源供给、海平面变化、古季风对三角洲的形成发育具有重要的控制作用。

The continental shelf area of the Yinggehai Basin in the northwestern of the South China Sea is an important tectonic unit bearing rich information on sedimentation and sea level changes since the Quaternary.Based on the interpretation of the high-resolution single-channel seismic profiling in this area,combined with the drilling data in the deep water area,the sedimentary characteristics of the Late Quaternary strata in the area were analyzed.The shallow stratum of the study area could be divided into two stratigraphic units:unit A and unit B.The seismic characteristics of the delta plain,delta front,and front delta in the study area were recognized and analyzed.The age-dating results using accelerator mass spectrometry ^(14)C and optically stimulated luminescence indicate that the delta formed during 65~56 kaBP of the Late Pleistocene.Combined with regional geology and sedimentary background,the control factors of delta formation were analyzed.It is believed that the structure and paleo-geomorphology of the Yinggehai Basin,the uplift of Hainan Island,the supply of provenance,and sea level change are important factors controlling the formation of delta.