Quaternary magnetostratigraphic study of the Ningbo area in Zhejiang using borehole Z03

A large amount of thick marine and continental sediments had deposited in the Ningbo area since the Quaternary, and its classification and comparison is vital to study of the Quaternary sedimentary environment. Borehole Z03 located in the southern Ningbo coastal plain reveals that the area contains several sedimentary cycles due to several transgressive-regressive activities, with variable lithologic characteristics and complicated sedimentary facies. Combined with lithological features, OSL and ¹⁴C dating data of the drilling core, the study established a reliable magnetic stratigraphic framework. The results show that all the samples of borehole Z03 fall into the Brunhes normal polarity zone, and record three global magnetic excursion events and one regional event, including Blake, Laschamp and Guthenberg events from bottom to top. 80.0～87.0 m deep samples record the Blake event occurring between Middle Pleistocene and Late Pleistocene, with the bottom of upper Pleistocene defined at a depth of 79.2 m. 42.2～44.0 m deep samples record the Laschamp event and 21.0～23.0 m deep samples record the Guthenberg occurring between Pleistocene and Holocene, with the bottom of Holocene located at a depth of 23.6 m.