南京——仪征地区新近纪地层层序及时代讨论

Stratigraphic sequence and age of the Neogene in the Nanjing-Yizheng area: a discussion

上世纪70年代以来,由于雨花台组与其他砂砾层之间接触关系未被发现,南京—仪征地区新近纪地层层序及时代一直存在着争议。笔者对仪征大仪集新仪1孔剖面进行了重新整理划分,新近纪各地层叠置关系明显,同时结合其他剖面及岩相古地理分析,在前人工作的基础上,对新近纪地层层序及时代进行了讨论。该地区新近纪地层层序为中新世中期的洞玄观组(N1d)、中新世晚期的六合组(N1l)、黄岗组(N1h)及上新世的雨花台组(N2y)以及非正式岩石地层单位方山玄武岩(fb)。雨花台组沉积是位于六合组之上的另一套砂砾层,其沉积时代为上新世晚期。

Since the 1970s, the stratigraphic sequence and age of the Neogene in the Nanjing-Yizheng area have long been controversial because the contact relationships between the Yuhuatai Formation and other sand-gravel beds have not been found. After restudy and division of the Xinyi No.1 hole section at Dayiji, Yizheng Town, the authors find that the superimposition relation of various strata of the Neogene is distinct. Based on this relation and previous work, combined with an analysis of other sections and lithofacies and paleogeography, the authors discuss the stratigraphic sequence and age of the Neogene. The stratigraphic sequence of the Neogene in the area includes the middle Miocene Dongxuanguan Formation (N1d), late Miocene Liuhe Formation (N1l) and Huanggang Formation (N1h) and Pliocene Yuhuatai Formation (N2y), as well as an informal lithostratigraphic unit-the Fangshan basalt (fb). The Yuhuatai Formation is another sand-gravel sequence overlying the Liuhe Formation and its age is late Pliocene.