Holocene sea-level change on the west coast Bohai Bay, China

Abstract. To constrain models on global sea-level change regional proxy data on coastal change are indispensable. Here, we reconstruct the Holocene sea-level history of the northernmost East China Sea shelf. This region is of great interest owing to its apparent far-field position during the late Quaternary, its broad shelf and its enormous sediment load supplied by the Yellow River. This study collected 15 sediment cores from the coastal plain of west Bohai Bay and extracted 25 sea-level index points through the analyses of sedimentary facies, foraminiferal assemblages and radiocarbon dating. These proxy data indicate a phase of rapid rise from c. −17 m to −4 m of mean sea level between c. 10 ka and 6.5 ka. This was followed by a phase of slow rise from 6.5 ka to 2 ka. In contrast to previous studies our data suggest that the sea level remained c. 2.5–1 m below the modern mean sea level during the mid-late Holocene. The difference between proxy data and sea-level predictions based on three GIA models suggests that the Bohai coastal plain experiences subsidence at a rate of around 1.25 mm/a since about 7 ka which masks the mid-Holocene highstand recorded elsewhere in the region. Thus, during the early Holocene rapid rise the sea flooded the coastal plain and the shoreline retreated landwards at a rate of c. 40 m/a. It stayed at the landward maximum marine limit during the mid Holocene when the sea-level rise slowed down allowing vertical sedimentary accretion to occur in the landward areas. During the late Holocene fluvial sediment supply outpaced the sea-level change and the shoreline prograded seawards at a rate between 20 and 10 m/a.