Sedimentary signatures of the abrupt deglacial rise in sea level from the East China Sea inner shelf

Abstract

Understanding the link between deglacial sea-level jumps and abrupt climate change may provide crucial insights into future ice-climate feedbacks. However, much ambiguity remains surrounding many of the last deglacial meltwater pulses. Here, we present a complete sedimentary succession from the inner shelf of the East China Sea, which has clearly documented multiple abrupt rises in the deglacial sea level. The results suggest that the postglacial sedimentary sequence, resting on a late Pleistocene basement of stiff clay, formed during a three-stage process marked by characteristic lithology and foraminiferal fauna. The abrupt shifts in the sedimentary facies indicate that seawater firstly intruded into the inner shelf just before the onset of the slowdown in sea-level rise caused by the Younger Dryas cooling event and changed the inner shelf into a tidal flat environment, as demonstrated by the sudden appearance of both planktonic foraminifera and typical brackish-water species of benthic foraminifera. Meltwater pulse 1B (MWP-1B) is depicted by a sharp upward transition to a nearshore subtidal environment at 11.62 kyr. This episode of sea-level rise induced the initial flooding of the inner shelf, which is well documented by the sudden reduction in brackish-water foraminifera species and evident increase in inner-shelf benthic species. The prominent sea-level rise at approximately 7.54 kyr was responsible for the shift to stable inner shelf conditions and resulted in the maximum flooding of the inner shelf area, initiating subsequent formation of the alongshore mud wedge. Additionally, obvious peaks in both the benthic foraminifer abundance and the marine algae concentration at approximately 8.13 kyr confirm the previously identified sea-level jump at approximately 8.2 kyr, which coincides with the weakening of the Asian monsoon demonstrated by the peak grain size in our record, further indicating its apparent connection to the 8.2 kyr climatic reversal.