Identification and significance of the Late Pleistocene transgressive strata in the bays of northern Fujian Province based on geochemical element indicators of sedimentary origin

The lack of micropaleontological records in the Late Pleistocene strata along the Fujian coasts has greatly restricted the further understanding on the regional land-sea interaction.This study aims to identify the transgressive strata of the Late Pleistocene in the two bays of northern Fujian, by using geo- chemical elements of sedimentary origin.Based on the analysis of the foraminifera and surficial sediments of Sansha Bay, the Sr/Ba and Mn/Fe are used as proxies to identify the possibility of transgression in the study area.The results suggest that there are three sets of dark grey layers in the two late Quaternary cores might be formed in a marine environment.Foraminifera are missed at the bottom of drilling cores in the open Xiapu Bay, while foraminifera are only observed in the upper drilling cores of semi-closed Sansha Bay.However, the sedimentary Sr/Ba ratios in the three clay layers are much higher than 1 and similar to the modern tidal flat and bay system, indicating typical marine origins.This is also supported by the occurrence of marine dinoflagellates and abundant authigenic pyrites in these layers.Based on the existing chronology of the core ( NDGK2 ) , the three transgressive layers are possibly corresponding to the high - stands of the M1S5 , M1S3 and M1S1 , respectively.The mean ratios of Sr/Ba and Mn/Fe show an increase trend from M1S5 to MiSl , indicating marine influence is enhanced compared with the ratios of modern tidal flat-bay system.This study shows geochemical elements of sedimentary origin can be used as an effective proxy to identify the Late Pleistocene transgression strata along the Fujian coast, which will help to further understand the process and controlling factors of the late Quaternary transgression in this area.