These datasets provide data for the lowest part of a new composite profile GOS18 from Lake Gościąż in central Poland. The composite profile was established using sediment cores recovered in 2015 and 2018 with an UWITEC Piston Corer at 19.6-21.5 m water depth (Bonk et al., in press). Our data covers the time interval from the onset of lacustrine sedimentation in the late Allerød to the early Preboreal. Since Lake Gościąż comprises a continuous, seasonally resolved (varved) and exceptionally well-preserved archive of the Younger Dryas (YD) climate variation, it is highly suitable for detailed investigations of lake system responses during periods of rapid climate cooling (YD onset) and warming (YD termination), respectively.Stable isotopes of oxygen in carbonates (δ18Ocarb) and of carbon in bulk organic matter (δ13Corg) were determined on bulk sediment samples contiguously taken at 0.5-1 cm resolution for the time interval from late Allerød to early Preboreal in Lake Gościąż (central Poland). All samples were freeze-dried, manually ground and homogenized, while samples for δ13Corg were additionally de-carbonized in situ. The dataset incorporates the composite depth and age [BP] for the sample midpoint, as well as the respective δ18Ocarb and δ13Corg values.

δ13Corg: Carlo Erba NC2500 elemental analyser coupled with a DELTAplusXL Isotope Ratio Mass Spectrometer (IRMS), GFZδ18Ocarb: KIEL IV carbonate device connected to a MAT253 Isotope Ratio Mass Spectrometer (IRMS), GFZ