Geochemical data (XRF-scanner) for core LC7 sediment record from Blaso, a large, epishelf lake in NW Greenland collected July-August 2017

The dataset comprises multi-proxy analyses of sediment core, LC7, extracted from Blaso, a large epishelf lake on the margin of 79 °N Ice Shelf, NW Greenland in July-August 2017. The data are used to constrain ice shelf dynamics over the last 8500 calibrated years before present (cal. years B.P., where present is A.D. 1950). A 2 m-long sediment core was recovered with a UWITEC KOL 'Kolbenlot' percussion piston corer to a total sediment depth of 3.74m. Core LC7: 87 m water depth; 79.589 ° N, 22.494 ° E. Geochemical data for the LC7 sediment records consists of XRF-scanner data. This project was funded by the Natural Environment Research Council (NERC) through Standard Grant NE/N011228/1. We thank the Alfred Wegner Institute, and particularly Angelika Humbert and Hicham Rafiq, for their significant logistic support through the iGRIFF project. Additional support was provided from Station Nord (Jorgen Skafte), Nordland Air, Air Greenland and the Joint Arctic Command. Naalakkersuisut, Government of Greenland, provided Scientific Survey (VU-00121) and Export (046/2017) licences for this work.

A 2 m-long sediment core was recovered with a UWITEC KOL 'Kolbenlot' percussion piston corer to a total sediment depth of 3.74 m (LC7) in Blaso (LC7: 79.589 °N, 22.494 °E, 87m). Prior to analysis sediment samples were treated with 20 % hydrogen peroxide to digest the organic material. Once the organic material has been digested the sample was centrifuged and then 20 ml distilled water plus 2 ml sodium hexametaphosphate was added to defloculate the sample. High-resolution elemental abundances were measured on the split core using a GEOTEK X-ray Fluorescence (MSCL-XRF) at 1 mm resolution. We use elemental ratios Ti/Ca as a proxy for terrigenous flux, while Mn/Fe and Br concentrations provides semi-quantitative information about lake oxygenation (Naeher et al., 2013) and marine organic carbon content (Ziegler et al., 2008) respectively. Ti contents in marine sediments is directly linked to terrigenous (siliciclastic) sediment supply delivered by fluvial and/or aeolian transport processes (Arz et al., 1999; Nace et al., 2014), while Ca concentrations reflect changes in the production of calcium carbonate (CaCO^3) by marine plankton (Bahr et al., 2005). High Ti/Ca ratios are indicative of an increased terrigenous flux. The behaviour of Fe and Mn is strongly dependent on processes of oxidation and reduction. Reducing conditions are the result of O2 consumption during organic matter (OM) remineralisation, which releases Fe and Mn. Because Fe oxidises faster than Mn, high Mn accumulation and thus high(low) Mn/Fe ratios reflect oxic (anoxic) conditions. Bromine (Br) is used as a proxy for marine organic carbon, since bromine is found at higher concentrations in marine, compared to terrestrial, organic matter (Ziegler et al., 2008; Seki et al., 2019).

UWITEC KOL 'Kolbenlot' percussion piston corer GEOTEK X-ray Fluorescence (MSCL-XRF)