DOI: 10.5285/6bd95602-f2e3-4968-8622-c4aeb71c214c
title: Geochemical X ray fluorescence log ratio time series data for two sediment cores, LP08 and LP16, extracted from Lago Pato, Torres del Paine, Southern Chile

description: The dataset comprises of X ray fluorescence log ratio time series data for two sediment cores from Lago Pato, a small lake basin at 51.3003 S, 72.6786 W and approx 33 m a.s.l., which is topographically separated from Lago del Toro in Torres del Paine (TdP). The data are used to constrain glacier dynamics and lake level change in the TdP and Ultima Esperanza region over the last approx 30,000 cal a BP (30 ka). LP08 was extracted from the current depocentre in November 2007 to March 2008. LP16 was extracted the terrestrial shoreline in November 2015. This project was funded by the Natural Environment Research Council (NERC) through the British Antarctic Survey (BAS) and an UGent BOF bilateral collaboration project. RMcC was supported by Programa Regional R17A10002 and R20F0002 (PATSER) ANID. We gratefully acknowledge the University of Magallanes (UMAG) and the University of Santiago (Carolina Diaz) for assistance with fieldwork; the NERC/SUERC AMS Radiocarbon Facility for providing initial range-finder radiocarbon dates; the NERC Isotope Geosciences Laboratory (NIGL, now National Environmental Isotope Facility, NEIF, at the British Geological Survey) and Melanie Lang for stable carbon isotope analysis; Aberystwyth University (David Kelly), Durham University (Neil Tunstall and Christopher Longley) and Edinburgh University (Chris Hayward) for use of their core scanning and microprobe facilities and technical support.
description: Chronology A chronology for each record was established using Accelerator Mass Spectrometry (AMS) radiocarbon dating of 21 samples from the LP08 record and 15 samples from the LP16 record. Calibration of radiocarbon ages was undertaken in OXCAL v.4.4 using the SHCal20.14C Southern Hemisphere atmosphere calibration curve (SH20). Radiocarbon ages are reported as conventional radiocarbon years BP (14C years BP) ±1sigma; and calibrated ages as 2sigma; (95.4%) ranges, median and mean calendar years BP (cal a BP and cal ka BP, relative to 1950 CE), rounded to the nearest ten years. Age-depth models were developed using Bayesian age-depth modelling software (rBACON v.2.5). Modelled age data mean ages produced by the SH20M1H (Southern Hemisphere, SHcal20, radiocarbon calibration curve) in rBACON, where M1 indicates Model 1 and H indicates the inclusion of a hiatus in the model. Geochemistry Sediment cores were collected using a UWITEC-gravity corer, Livingston piston corer and a Russian corer from the deepest point (approx 3.5 m of water depth) in Lago Pato: - LP08 record from 51.3003 S, 72.6786 W, 32 m a.s.l. is 600 cm long - LP16 record from 51.3031 S, 72.6816 W, 33?34 m a.s.l. is 295 cm long Contiguous downcore wet-sediment Energy Dispersive Spectrometry (EDS) X-ray fluorescence core scanning (XRF-CS) data was collected using an ITRAX XRF core scanner at Aberystwyth University fitted with a Molybdenum (Mo) anode X-ray tube (settings: 30 kV, 50 mA, count time 10 seconds, at 2 mm contiguous intervals and for LP08 Unit 6 (equivalent to mean ± 2-sigma: 4.5±7.0 years), at 200 micrometers intervals for LP08 Unit 1 (1.3±4.2 years), with LP08 basal Unit 1 scanned at 100 micrometers, and at 500 micrometers for LP16 Units 2-6 (9.6±17.4 years) and at 200 micrometers for LP16 Unit 1 200 micrometers (1.1±1.6 years). Data from finely laminated glaciolacustrine sediments in Units 1-2 were measured at or smoothed to 200 micrometers (from 100 micrometers interval data) before analysis. Time series analysis Log-n element/Ti ratio XRF-CS Z-scores were used for time series analysis (Fast Fourier Transform FFT, periodograms, Lomb-Scargle Power Spectrum, Wavelet Power Spectrum, Peak Identification) in MATLAB. Equally spaced (10-year and 100-year) time-intervals were generated using a Piecewise Cubic Hermite Interpolated Polynomial (PCHIP) function, which avoids spline artefacts and preserve the shape of the original XRF-CS data series (Grinsted et al., 2004; Trauth, 2015). Time series data were detrended (polynomial linear best fit) to remove the long-term linear trend. Second order polynomial Locally Weighted Scatterplot Smoothing (LOESS) 100-year smoothing (0.1 sampling interval with outliers removed) was also used to compare datasets to published data. Data were analysed in MATLAB v. R2021a, R v. 4.1.0/Rstudio v. 1.4.171, using the R packages Vegan, Rioja, Tidyverse, ggplot2, Ggally v. 2.1.2. Code is available from: https://github.com/stever60/Lago_Pato
description: XRF-CS data from finely laminated glaciolacustrine sediments in Units 1-2 were smoothed to 200 micrometers, other data to 2mm, and equal spaced time-intervals (10-years and 100-years) for use in time series analysis were generated. Time series datasets were centred, standardised (Z-scores), detrended and interpolated using a 10-year or 100-year Piecewise Cubic Hermite Interpolating Polynomial (PCHIP) function, which avoids spline artefacts and preserve the shape of the original XRF-CS data series.