Magnetic properties of minerals recorded by the borehole WJ and Late Quaternary transgressions in the Taihu plain, southern Yangtze Delta

Based on paleomagnetism and AMS¹⁴C ages, we reconstructed the evolution of sedimentary environment and transgression events during the Late Quaternary by examining the lithology, magnetic properties, grain sizes, and foraminifera of sediments from a borehole named WJ in the Taihu plain, southern Yangtze Delta, China. We also examined the applications of magnetic proxies to distinguishing depositional environments in the estuary-delta area. The results show that the sediment sequence of the WJ borehole can be divided into four periods, i.e. Mid-Pleistocene stage I, Mid-Pleistocene stage II, Late-Pleistocene, and Holocene. Their depositional geomorphological conditions were fluvial-lacustrine, coastal-terrace, mouth bar-estuary-tidal flat-terrace, and lacustrine plain, respectively. Three transgression events were detected in the borehole WJ, which happened during the late Mid-Pleistocene, MIS5 and MIS3 of Late-Pleistocene. Among them, the MIS5e transgression was the strongest one. Additionally, the transgression was intensified significantly in late MIS3. Magnetic properties were strongest for the tidal flat and mouth bar sediments with notably high values of χ_lf, SIRM and HIRM.