Stratigraphic and paleomagnetic characteristics revealed by the J9 hole in the north flank of the Yangtze River delta

Abstract：Quaternary land and sea shift and environmental evolution with a relatively long duration on the north flank of the Yangtze River delta are lacking in a deep-going study. A 423 m deep hole, named J9, was drilled in bed rocks at Hai'an County of the Yangtze River delta, which provides a good research target. Based on observations of its core in the loose bed and summarizing the sedimentary characteristics, it is evident that this core may be divided into six characteristic lithological intervals. In addition, the paleomagnetism data of the strata suggest the following： the interval 0-200 m belongs to the Brunhes normal polarity epoch, the interval 200-334 m to the Matuyama reverse polarity epoch, and the interval below 334 m depth to the Gauss normal polarity epoch. Through an integrated analysis of the sedimentary characteristics of the core and by referring to the results of the paleomagnetic measurements, the authors made a preliminary stratigraphic division and think that： the interval 0-39 m is Holocene strata, the interval 39-153 m Late Pleistocene strata, the interval 153-200 m middle Pleistocene strata, the interval 200-334 m early Pleistocene strata and the interval below 334 m depth Neogene strata. There is a late Pleistocene hard clay marker bed, which indicates that the postglacial river valley was not developed in this area.