Quaternary multistratigraphic study of Borehole ZK10, Xinghua, Jiangsu Province

Borehole ZK10 is located in Xinghua City, Jiangsu Province. Based on litho-, bio-, magneto- and chronostratigraphic study of the core sediments, the authors established its Quaternary chronological framework: ①The lower boundary of Quaternary, consistent with the G/M boundary at 2.58Ma, was found at 212m in depth. The Lower Pleistocene in this core was composed of the lower, middle members and lower to mid-parts of the upper member of the Wuduizhen Formation, and corresponded to the pollen zones Ⅰ-1 and Ⅰ-2. ②The Early/Middle Pleistocene boundary, in accord with the M/B boundary at 0.78Ma, was found at 120m. This was defined at the boundary between the pollen zones Ⅰ-1 and Ⅱ. The Middle Pleistocene was composed of the top part of upper member of Wuduizhen Formation and the lower member and the lower- to mid-parts of the upper member of the Xiaoyaozhuang Formation. The Wuduizhen Formation was a time-transgressive lithostratigraphical unit across the Lower/Middle Pleistocene. ③The Middle/Late Pleistocene boundary at 120ka BP was found at the depth of 81.5m. It lay on the boundary between the pollen zones Ⅱ and Ⅲ-1, and essentially coincided with the boundary between Xiaoyaozhuang Formation and Guannan Formation. The latter was another timetransgressive unit crossing both the Middle and Upper Pleistocene. The Upper Pleistocene was composed of the pollen zones Ⅲ-1, Ⅲ-2, Ⅳ and Ⅴ. ④The Late Pleistocene/Holocene boundary, about 10ka BP, 12.25m, lay on the pollen boundary between zones Ⅴ and Ⅵ. Lithostratigraphically, Holocene deposits belong to the Yujian Formation and correspond to the pollen zone Ⅵ.