Radiocarbon dating of sediments from Lake Żarnowieckie (North Poland)

This study aims to establish the chronology of lower sediment deposition in Lake Żarnowieckie, a glacial-origin lake located in the coastal zone of the Baltic Sea in northern Poland, through radiocarbon dating. An 8-meter-long sediment core was extracted from the lake’s bottom. Then, 21 samples of the bulk sediment, as well as plant remains, were selected from the layers of visible lithological borders. The samples underwent ABA chemical preparation and were subsequently processed into graphite for analysis using the MICADAS accelerator mass spectrometer at the ¹⁴C and Mass Spectrometry Laboratory in Gliwice. A total of 20 dating results, ranging from 2,300 BP to near the limit of the radiocarbon method were obtained. Comparison of these results with expert palynological and lithological analyses indicated that 12 dates were overestimated due to the reservoir effect and redeposition of older material. The reservoir effect in Lake Żarnowieckie is estimated at several hundred to 2,000 years, consistent with findings from other Polish lakes. Two samples showed particularly large age discrepancies compared with the age-depth model, suggesting the possible redeposition of older material and sedimentation disturbances, such as sublacustrine landslides or increased erosion. Additionally, two samples (with ages approaching the radiocarbon method limit) originated from deep, sandy layers that were likely deposited by glacial processes before the formation of the lake. The remaining six dates were considered reliable and were subsequently used to construct the age–depth model. The sedimentation rates derived from the model vary distinctly between lithological units.

Research supported by EU funds FSD – 10.25, Development of Higher Education Focused on the Needs of the Green Economy, European Funds for Silesia 2021–2027: The modern methods of the monitoring of the level and isotopic composition of atmospheric CO2 (project no. FESL.10.25-IZ.01-06C9/23-00). This research was partially funded by the Polish Geological Institute, National Research Institute (Grant No. 62.9012.2309.00.0), and partly by the NCN Project, Opus 23 (UMO-2022/45/B/ST10/03167) and Opus 29 (2025/57/B/ST10/03700).