Sedimentary mercury measurements for core ICDP DEEP 5045-1, Lake Ohrid

The datasets include raw and corrected measurements of mercury in sediment samples from core DEEP 5045-1 extracted from Lake Ohrid in 2013, as part of the ICDP-funded project: Scientific Collaboration on Past Speciation Conditions in Lake Ohrid (SCOPSCO). Lake Ohrid (41° 02′ N, 20° 43′ E) is a tectonic lake situated 693 m above sea level in south-east Europe. The ~447 m-long sedimentary succession extracted from the DEEP (central) site provides a continuous record of hemipelagic sediment accumulation since ~1360 ka, with age control provided by combining tephrochronological data from 16 Ar/Ar dated tephra layers, magnetostratigraphic data, and orbital-tuning of peaks in total organic carbon. Paine et al. (2024) analysed sedimentary Hg concentrations in the top 36 m of the DEEP 5045-1 sediment succession. Here, this dataset is extended to cover the full 447 m succession, with Hg measurements taken for 640 powdered bulk sediment samples between 36 and ~447 m composite depth at a sampling resolution of 64 cm (or an average of ~2000 years). Total Hg concentrations (HgT) were measured using a RA-915+ Portable Mercury Analyzer with PYRO-915+ Pyrolyser, Lumex (Bin et al., 2001) at the University of Oxford. In Lake Ohrid, endogenic calcite (CaCO3{~}) accounts for up to >80% of the total sediment carbonate mass with small contributions from biogenic and detrital terrigenous calcium carbonate. Such a high and variable carbonate content creates a high risk of Hg fluxes to the sediment being diluted, and the variability results in a positive correlation to other diluted phases (TOC, TS, quartz, clay minerals), when this effect is not suitably accounted for. Also included are details for each standard sample analyzed in conjunction with the DEEP 5045-1 samples, in order to calibrate the instrument, and thus calculate integrated Hg concentration values.