To investigate the depositional environment evolution and controlling factors of a mountainous river estuary during the Holocene,in this study it selected a drilling core(MLX-S)from the river mouth of Mulanxi,a tidal-controlled mountainous river in central Fujian Province,China.The core was subjected to radiocarbon dating,optically stimulated luminescence dating,grain size analysis,XRF core scanning,and ICP-OES elemental measurements.During the Holocene,the Mulanxi estuary experienced a transition from fluvial facies to riparian marsh facies,shallow marine facies,and finally to tide-controlled estuarine facies.The sedimentary environment evolution was primarily influenced by relative sea-level changes in the study area.The relative sea level along the coast of central Fujian is around 9.0 ka and about-20 m.Subsequently,the marine transgression reached the strongest and the maximum sea level occurred around 5.8 ka,followed by a slow decline till the present.High-resolution XRF core scanning data,after calibration of element relative intensities,can indicate sediment provenance and paleoenvironmental changes.The downcore variation of K/Ti ratio suggests that since 8.8 ka,the sediments in the Mulanxi Estuary were mainly derived from a mixture source of local basin erosion and fine offshore material from the Changjiang(Yangtze River).The core Fe/Ti ratio reached its peak in four strong East Asian winter monsoon periods of about 3.6 ka,4.3 ka,5.4 ka and 6.0 ka,corresponding to periods of strong East Asian winter monsoon,which is consistent with the sedimentary records on the East China Sea inner shelf and tightly related to the changes of Min-Zhe coastal current intensity.This study reveals the typical river-sea interaction in the tide-controlled mountainous estuaries along the southeastern coast of China,and suggests the complex source-sink transport processes of Changjiang-derived fine sediments on the continental shelf driven by the Holocene monsoon and sea level changes.This study also promotes the potential application of XRF core scanning in the continental margin where has the unique sedimentary dynamics and environmental changes.
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