Sediment core (gravity core) HH14-897-GC-MF was collected from Brepolen Bay, inner Hornsund, Svalbard (76°59.555' N; 016°24.313' E), from a water depth of 125 m, on 2014-10-18, during R/V Helmer Hanssen cruise. The total core length was 154 cm. The sampling site was located in a glacial bay formed after the termination of the Little Ice Age (Strzelecki et al., 2020, doi:10.1002/esp.4819). The dataset with raw data on gamma spectrometry measurements of excess 210Pb and 137Cs, total organic carbon (TOC) content, and delta 13C isotopic ratio of bulk organic matter is presented by Szczuciński et al. (2022, doi:10.1594/PANGAEA.946568). Here is presented an age model based on the constant flux constant sedimentation rate (CFCS) model verified with 137Cs peaks. The data were obtained within a National Science Center (Poland) project: 'Impact of post-Little Ice Age glaciers retreat on sediment accumulation and carbon burial rates in subpolar fjords' and presented during conference presentations (e.g., Szczuciński et al. 2017). The excess 210Pb and 137Cs data were measured in the Institute of Geology at Adam Mickiewicz University in Poznań, Poland using a gamma detector Canberra BE3830 (Szczuciński, submitted). The model was calculated using serac code (Bruel and Sabbatier, 2020, doi:10.1016/j.jenvrad.2020.106449).