摘要
本文以生物事件的观点论述和探讨了上新统一更新统界线在南海北部的划分。南海北部陆架有跨越上新统一更新统界线的海相地层,其中莺歌海一琼东南盆地的海相第四系厚达2000m左右,是我国除台湾省外研究海相更新统下界的最佳地点。该盆地钻孔中的浮游有孔虫与钙质超微化石群的垂向序列,与意大利Vrica上新统一更新统界线国际层型剖面可以对比,得出1.64Ma的界线值,但在界线上下岩性和化石群均无明显变化,难以在实践中使用。相反,界线下的Globorotalia multicamerata sensu lato末现面上下,浮游有孔虫占有孔虫全群的比例和壳体保存状况发生剧变,地震剖面上亦显示下削上超的接触关系,代表着大约2.00—2.50Ma前一个重要的沉积间断面,此面还可追索到珠江口盆地和北部湾盆地。西太平洋等地海相地层中与此期相应也有明显的沉积环境变化。为此,建议以此面作为划分南海北部上新统一更新统的界线。
A marine stratigraphic sequence crossing the Pliocene/Pleistocene boundary has been found in the northern continental shelf of the South China Sea. The marine Quaternary deposits in the Yinggehai Basin may exceed 2,000m in thickness, probably providing the best section for studying the lower boundary of the marine Pleistocene in South China. The vertical succession with planktonic foraminifers and nannofossils revealed in bore-holes in the basin has been well correlated with that in the international stratotype section of the Pliocene/Pleistocene boundary at Vrica, Italy, resulting in the acquirement of a biostratigraphic boundary at 1.64 Ma. BP. This boundary, however, does not oincide with any prominent lithological or palaeontological changes in the study area and can hardly be used in geological practice. There are, in contrast, significant changes at the level of LAD of Globorotalia multicamerata s. l. located below the above-mentioned boundary. The percentage of planktonic foraminifers in the total population and the preservation of foraminiferal tests display great changes at this level corresponding to a clear onlap on the seismic profiles and indicating a depositional hiatus of ca. 2.0—2.5 Ma. Since the level can be widely traced in the Pearl River Mounth Basin and the Beibu Gulf Basin and well corresponds with the marked deposition-environmental changes recorded in the west Pacific and other regions, it is recommended that the Plio/Pleistocene boundary be drawn at the level of Gr. multicamerata s. l. LAD, roughly concurrent with the Gauss/Matuyama turn.
出处
《地质学报》
EI
CAS
CSCD
北大核心
1991年第2期176-187,T001,共13页
Acta Geologica Sinica
基金
国家教委科学基金
