DOI: 10.1594/pangaea.987515
title: Geochemical composition (corrected) of the Late Holocene sediments core LV66-3 (Amur Bay of the Sea of Japan) and result of paleoclimatic reconstructions

description: Sediment core LV66-3 (43°07,473' N,131°49,622' E length of 466 cm; water depth 33 m) was collected in 2014 during the 66th cruise of the R/V Akademik M.A. Lavrentiev in the Amur Bay of the Sea of Japan using a gravity core. The sampling location was chosen in the zone of maximum bottom water hypoxia (Tishchenko et al., 2011), which ensured minimal bioturbation of sediments due to oppression of benthic fauna. Continuous seismic profiling data at this site revealed a homogeneous structure of the sedimentary strata, with no visible breaks in sedimentation and no inclusions of sediments of a different composition (Karnaukh et al., 2016).The sediments of core LV66-3 are represented by monotonous clays and silty clays of black or dark gray color without visible stratification, with slightly varying density and humidity (Akulichev et al., 2015; Karnaukh et al., 2016). The analysis of the prepared samples was performed in the Budker Institute of Nuclear Physics (Novosibirsk) using a scanning X-ray fluorescence analyzer with the synchrotron radiation (XRF SR ) at the VEPP-3 storage ring as the excitation source according to previously developed methods (Darin et al., 2005; 2015; Kalugin et al., 2007; 2015). The scanning step was 0.5-0.8 mm. The concentrations of Ca, K, Ti, Mn, Fe, V, Cr, Ni, Cu, Zn, Mo, Pb, Rb, Ba, Sr, Y, Br, As, and Nb were determined. The detection limits for the elements were (mg/g): 0.5 (Br, Rb, Sr, Nb), 1 (Zr, Y), 2 (Zn, Ni, Mn, Pb), 10 (Fe), 15 (Ti), and 100 (Ca, K) (Kalugin et al., 2015). Rubidium-normalized elements were used for dimensionless variation. The age model of core LV66-3 was based on radiocarbon dates, tephrochronological data, and chemostratigraphy. Calibration of the 14C dates to obtain the calendar age of the studied samples was performed with the Calib program (Stuiver and Reimer, 1993) using the Marine13 calibration curve (Reimer et al., 2013). Correction of the reservoir effect was made using the dating of shells from Novik Bay in the eastern part of the Amur Bay (Kuzmin et al., 2001). Geochemical time-series were created using a methodology previously developed for Siberian lakes (Kalugin et al., 2007; 2013; Darin et al., 2005; 2015; Hildebrandt wet al., 2015; Babich et al., 2015; Rudaya et al., 2016) based on the results of XRF SR scanning of the core in the 0-466 cm interval and its age model with some additions that have been used in paleoreconstructions of shelf sediments in the Arctic seas (Astakhov et al., 2019; 2020; 2023). Considering the feature accumulation of sediment in the Amur Bay (Tishchenko et al., 2006; 2011, Akulichev et al., 2016;, Kalugin et al., 2015) and the experience construction of transfer geochemical functions for other areas (Kalugin et al., 2005; 2013; Babich et al., 1980; 2023; Astakhov et al., 2019; 2023), some elements were removed from the initial feature space: Zr, Nb, and Y are significantly enriched in the tephra of the Baitoushan volcano and overlying sediments, molybdenum is the element with maximum response to redox conditions, lead and zinc are possible anthropogenic contaminants in the surface sediment layer (Kalugin et al., 2015), and elements with very low content and weak variability. The final processing of the remaining 14-element XRF SR scan data matrix (this table) for the construction of transfer functions and paleoclimatic reconstructions was carried out in the following order:- removal of sampling intervals containing instrumental errors, coinciding with layers of different composition (pyroclastics), and showing signs of intense diagenetic transformations; for these reasons, geochemical data for layers 352-363, 372-380 and 426-466 cm were removed;- correction of the content of elements that give anomalous extremes due to the presence of fragments of plant remains, shells and minerals in the sedimentary layers; in these cases, the anomalous contents of chemical elements were replaced by the values obtained by interpolation taking into account their contents in the four nearest sampling points (two from above, two from below);- generate fractional time-scale geochemical series by transferring geochemical information from the linear scale to the time scale corresponding to the age model of the core; - reduction of time series with a fractional time scale to an integral annual time scale with their subsequent smoothed using an 11-year moving average (hereafter referred to as decadal averages);- rubidium normalization of the chemical elements content (this table);- minimax normalization of chemical elements (this table), which makes it possible to bring them into a comparable form, regardless of the scale of their measurement.