Comparison and Calibration of Elemental Measurements in Sediments Using X-Ray Fluorescence Core Scanning with ICP Methods: A Case Study of the South China Sea Deep Basin

The X-ray fluorescence(XRF)core scanning method is widely applied in studies of sedimentary paleoenvironments due to its convenient pretreatment,nondestructive characteristics,fast execution,continuous scanning,and high resolution.XRF core scanning for sediments is commonly used in the studies on the South China Sea.This study compares XRF-scanned intensities and measured inductively coupled plasma(ICP)elemental contents of core CS11 in the northeast South China Sea deep basin.The results show that the analyzed elements can be separated into three classes.Class I includes elements with high correlation coefficients,such as Ca,Sr,and Zr;Class II contains elements with average correlation coefficients,such as Fe,Mn,Ti,and Cu;and Class III comprises elements with low correlation coefficients,such as K,Ni,Zn,Rb,and Al.In the South China Sea deep basin,pore water,compaction,and grain size have weak effects on the elemental intensities and contents of short core sediments.Hence,for elements with high correlation coefficients,a linear relationship model can be established by the least-squares method,in which the converted XRF intensities are approximately equal to the measured ICP contents.Based on the established log-ratio calibration model,the resulting ln(K/Ca),ln(Ti/Ca),ln(Fe/Ca),and ln(Zr/Ca)values generally display the same variation trends as the measured curves.The elemental contents and ratios produced by the linear model via the least-squares method and the log-ratio calibration model are expected to provide high-resolution data support for future paleoenvironmental research on the South China Sea deep basin.

Dated deposition couplets link catchment erosion flux with storm discharge on the Chinese Loess Plateau

Tracing erosion flux within a single catchment is one of the major targets for the Earth's Critical Zone science. The sedimentary succession in landslide-dammed reservoirs within the Chinese Loess Plateau(CLP) serves as a valuable archive of past erosion history. Deposition couplets and annual freeze–thaw layers were firstly identified for the sedimentary succession of the Jingbian reservoir on the northern CLP with high-resolution XRF core scanning. The deposition couplets in the reservoir since 1963 A.D. were further dated with ^(137) Cs activity. We found consistent one-to-one correspondence between couplet specific sediment yield and storm intensity. The reconstructed soil erosion history highlights the control of storm intensity and frequency on loess erosion on the northern CLP in the past hundreds of years.

High-Resolution Geochemical Records in the Inner Shelf Mud Wedge of the East China Sea and Their Indication to the Holocene Monsoon Climatic Changes and Events

The inner shelf mud wedge(ISMW)located in the East China Sea(ECS)is the fine-grained sedimentary area with high sedimentation rate and has provided an ideal study area for understanding the East Asian Summer Monsoon(EASM)evolution during the Holocene.In this paper,we presented the high-resolution geochemical data of the sediments from the core MD06-3040 in the ISMW of the ECS determined by X-ray fluorescence core scanning(XRF-CS)analysis,a high-resolution,continuous,and multielement method.Geochemical and factor analysis results reveal that the variations of elemental compositions(Al,Si,K,Ti,Fe),the elemental ratios of Al/Zr,Ca/Ti and Rb/Sr,and the factor scores(F1 are correlated with the changes of the EASM during the period of 6000–1300 cal yr BP.The higher values of geochemical compositions indicating the terrigenous inputs implied the intensification of anthropogenic activities after 1300 cal yr BP.Meanwhile,the significant decrease of most geochemical compositions and the F1 factor scores during 4500–3500 cal yr BP and 1700–1500 cal yr BP,within the dating errors,coincided with the weak EASM events(presumably drought and cold events).The spectral analysis results of K concentrations,Al/Zr ratios and F1 factor scores show the millennial and centennial climatic fluctuations,which are consistent with other marine sedimentary records in the adjacent areas.All the findings show that the geochemical compositions of sediments from core MD06-3040 are influenced by the EASM evolution,the variable El Niño/Southern Oscillation(ENSO)and the local oceanic thermohaline circulation(e.g.,Kuroshio Current).These results are greatly helpful in uncovering the forcing mechanism of the monsoonal climate in the east China over the Holocene and also contribute to the understanding of EASM variability.

Paleoclimatic indication of X-ray fluorescence core-scanned Rb/Sr ratios: A case study in the Zoige Basin in the eastern Tibetan Plateau

The X-ray fluorescence(XRF)core-scanned Rb/Sr ratios of lake sediments have been widely used as a proxy for chemical weathering intensity and past climate change.However,some factors could affect Rb/Sr ratios,causing misinterpretation and limiting its application.In this study,we present a high-resolution XRF core-scanned Rb/Sr record of core ZB13-C1 from the Zoige Basin in the eastern Tibetan Plateau.To validate its application,we correlated this record with the chemical index of alteration(CIA)and other paleoclimatic proxies.Our results showed that(1)the core-scanned Rb/Sr ratios and CIA were reliable proxies of chemical weathering intensity in fine-grained sedimentary sequences;(2)the low values of corescanned Rb/Sr ratios and CIA were significantly correlated with high total organic carbon content,arboreal pollen content,carbonate content,and C/N ratios,confirming its reliability as a proxy for the Asian summer monsoon intensity;(3)the corescanned Rb/Sr ratios at core depths of 25–0.3 and 56–47 m were unable to reliably reflect chemical weathering intensity due to both the grain-size effect and the low test accuracy.Our study highlights the need for mutual verification of multiple indicators before accurately applying Rb/Sr as a paleoclimatic proxy in other similar study areas.