The long transition from deltaic tidal flats to flood plains in the Pearl River delta

Abstract

To understand how coastal wetlands have evolved from mudflat emergence, vegetation colonization and floodplain formation in relation to the lowering sea level, deltaic progradation, decreasing water salinity and strengthening fluvial process during the late Holocene, this study analyzed five sediment cores from the head area of the Pearl River delta, southern China. The records of microfossil (diatom and pollen) assemblages, geochemistry (TOC and δ¹³C) and radiocarbon dating from these cores reveal the evolutionary history from delta front formation to delta plain formation, and particularly the transition from tidal mudflats to floodplains. This evolutionary history suggests that delta plain sedimentation in this area mainly started later than 4000 years ago, in response to the lowering relative sea level. The transition from the onset of tidal wetlands to the formation of deltaic levee-floodplain system has taken a couple of thousands of years due to the low sediment supply from the Pearl River and the persistent tidal force. In addition, the weak tidal saltwater intrusion into the head delta limited mangrove colonization on the mudflats over the past 4000 years. These details provide new insights for future management of coastal wetland resources and ecological restoration.