Constraining the transgression history in the Bohai Coast China since the Middle Pleistocene by luminescence dating

Abstract

Three phases of transgression have been identified in the Middle to Late Pleistocene sedimentary succession in the Bohai Sea, northern China, which is considered to be key information for understanding environmental evolution and marine-terrestrial interaction in the East Asia. However, the timing of these transgressions still remains controversial. In this study, luminescence dating was performed on a core drilled in the North Bohai Coast to establish a reliable chronological framework of the transgression-regression cycles. After validating the applicability of luminescence dating for the Bohai sediments, quartz optically stimulated luminescence (OSL) and K-feldspar post-infrared (IR) IRSL (pIRIR) signals with elevated temperatures at 150, 225 and 290 °C were employed for dating the sediment core. The quartz OSL signal used for the upper 25 m of the sediment core was well-bleached, yielding finite ages within ca. 50 ka, whilst the K-feldspar pIRIR225 signal was also well-bleached for the Pleistocene samples with an extended dating limit to ca. 300 ka. The luminescence ages of ca. 200 ka and ca. 7.0–0.2 ka indicated that the lowermost and uppermost of three transgression units likely represent sea-level highstand during Marine Isotope Stages (MIS) 7 and 1, respectively, which were also evidenced by the consistency between the reconstructed palaeo-topography elevation and the contemporaneous global mean sea-level. Our luminescence ages of the second transgressive unit suggest it has a MIS 3 origin, being consistent with previous studies, but this appears to be unlikely as the level of the unit is significantly above the interstadial sea-level in the MIS 3. Further high-resolution luminescence dating of the second transgression is thus required.