长江三角洲北翼J9孔岩芯沉积特征及地层初步划分

长江三角洲北翼地区缺少较长尺度的第四纪海陆变迁及环境演变的深入探讨，深达423m的海安县基岩标J9孔为此提供了较好的研究对象。通过观察该孔松散层岩芯，总结其沉积特征，认为岩芯明显可划分为6个特征岩性段。同时，地层古地磁测试结果显示：   0～200m为布容正极性世，200～334m为松山负极性世，334m以下为高斯正极性世。综合分析岩芯沉积特征并参考古地磁测试结果对地层进行了初步划分，认为 0～39m为全新世地层，39～153m为晚更新世地层，153～200m为中更新世地层，200～334m为早更新世地层，之下为新近纪地层。从沉积地层特征推测，在第四纪地层中可能存在有5个海侵层，自上而下为第Ⅰ海侵层（镇江海侵）、第Ⅱ海侵层（滆湖海侵）、第Ⅲ海侵层（昆山海侵）、第Ⅳ海侵层（嘉定海侵）和第Ⅴ海侵层（如皋海侵），分别出现在孔深 5～39m段、59.2～85.1m段、121～153m段、171～200m段和 246.3～277.2m段。孔深39～41m存在的晚更新世晚期特征硬粘土标志层，指示本地不是冰后期古河谷的发育地。

PRELIMINARY STUDY ON SEDIMENTARY CHARACTERISTICS AND STRATUM DIVISION OF J9 CORE IN THE NORTH WING OF THE YANGTZE RIVER DELTA

The J9 hole was drilled 423m deep at Hai′an  County，Jiangsu Province in East China，which is located in the north wing area of the Yangtze River delta. This hole core provides a good object for discussion on land sea interaction history in a long Quaternary period. Sedimentary characteristics of the core show that the stratum could obviously be divided into 6 lithological sections. 755 samples are collected at an interval of about 50cm for paleomagnetism and magnetic susceptibility testings. The paleomagnetism testing results indicate that the section between 0～200m belongs to Brunhes normal polarity chron，200～334m the Matuyama reverse polarity chron，below 334m the Gauss normal polarity chron. In summary，the section between 0～39m belongs to Holocene，39～153m the Late Pleistocene，153～200m the Middle Pleistocene，200～334m the Early Pleistocene，and below 334m the Neogene. The Quaternary stratum of this area recorded five transgression events，from up to down，the Zhenjiang transgression，the Gehu transgression，the Kunshan transgression，the Jiading transgression，and the Rugao transgression. There exists a characteristic stiff clay of Epipleistocene late period in the stratum，which indicates that the local area is not the growth place of the ancient river valley during the postglacial period.