Geochemical data for the upper 300cm of giant piston core MD04-2832. Core MD04-2832 was collected from the middle basin of Loch Sunart a fjord on the west coast of Scotland from the research vessel Marion Dufresne on the 15th of June 2004. This data resource includes five data sheets: (1) Geochemical data, (2) Bulk radiocarbon, (3) ICP-MS, (4) FRUITS and (5) Age Model. 1. Geochemical data sheet includes Bulk elemental data (Organic Carbon, Nitrogen, C/N ratio, N/C ratio), Isotopic data (δ13C and ẟ15N), Biomarker data (Alkanes, Fatty Acids, GDGT's) and thermosgravimetric data (% labile, recalcitrant and refractory organic matter). 2. Bulk Radiocarbon data sheet includes bulk radiocarbon data for ten sediment samples presented as % modern, 14C Age (years BP), ẟ14C and Δ14C. 3. ICP-MS data sheet includes metal data associated with mining activities within the fjords catchment. Data includes Zinc (Zn), Lead (Pb), Copper (Cu), Barium (Ba), Aluminium (Al) and elemental ratios of these metal normalized with Al concentrations. 4. The FRUITS data sheet contains the outputs from the FRUITS Bayesian isotopic mixing model (Fernandes et al., 2014) used to constrain the source (terrestrial vs marine) of the organic carbon found at site MD04-2832. The model used bulk elemental ratios (N/C), Isotopic (δ13C and ẟ15N) and biomarker data (GDGT - BIT Index) to calculate the terrestrial and marine OC fraction from each downcore sample. 5. The Age Model datasheet contains the age model produced by the BACON software package (Blaauw and Christen, 2011). The age model was developed with a combination of shell/foraminifera radiocarbon dates and radiometric dating (210Pb and 137Cs). Further details on the data can be found in Smeaton, C., Cui, X., Bianchi, T.S., Cage, A.G., Howe J.A., Austin, W.E.N., (2021), The evolution of a coastal carbon store over the last millennium, Quaternary Science Reviews.