Description: We present new annual sedimentological proxies and sub-annual element scanner data from the Lago Grande di Monticchio (MON) sediment record for the sequence 76-112 thousand years before present (ka). They are combined with the previously published decadal to centennial resolved pollen assemblage in order to provide a comprehensive reconstruction of six major abrupt stadial spells (MON 1-6) in the central Mediterranean during early phase of the last glaciation. These climatic oscillations are defined by intervals of thicker varves and high Ti-counts and coincide with episodes of forest depletion interpreted as Mediterranean stadial conditions (cold winter/dry summer). Our chronology, labelled as MON-2014, has been updated for the study interval by tephrochronology and repeated and more precise varve counts and is independent from ice-core and speleothem chronologies. The high-resolution Monticchio data then have been compared in detail with the Greenland ice-core d18O record (NorthGRIP) and the northern Alps speleothem d18Ocalcite data (NALPS). Based on visual inspection of major changes in the proxy data, MON 2-6 are suggested to correlate with Greenland stadials (GS) 25-20. MON 1 (Woillard event), the first and shortest cooling spell in the Mediterranean after a long phase of stable interglacial conditions, has no counterpart in the Greenland ice core, but coincides with the lowest isotope values at the end of the gradual decrease in d18Oice in NorthGRIP during the second half of the Greenland interstadial (GI) 25. MON 3 is the least pronounced cold spell and shows gradual transitions, whereas its NorthGRIP counterpart GS 24 is characterized by sharp changes in the isotope records. MON 2 and MON 4 are the longest most and pronounced oscillations in the MON sediments in good agreement with their counterparts identified in the ice and spelethem records. The length of MON 4 (correlating with GS 22) supports the duration of stadial proposed by the NALPS timescales and suggests ca 500 yr longer duration than calculated by the ice-core chronologies GICC05modelext and AICC2012. Absolute dating of the cold spells provided by the MON-2014 chronology shows good agreement among the MON-2014, the GICC05modelext and the NALPS timescales for the period between 112 and 100 ka. In contrast, the MON-2014 varve chronology dates the oscillations MON 4 to MON 6 (92-76 ka) ca. 3,500 years older than the most likely corresponding stadials GS 22 to GS 20 by the other chronologies.

Description: Here we provide the data set of fire proxies from the 77 ha, 32 m deep Lake Czechowskie (53°52′27″N 18°14′12″E, 109 m a.s.l.), northern Poland. The sediment core JC11-K5 was recovered in 2011 in 30 m water depth using an UWITEC gravity corer. JC11-K5 was dated by correlating ten macroscopically visible layers with counted annual layer sequences of adjacent cores and tephra shards related to the Askja eruption in 1875 CE. As a conservative estimate, we assigned a 2σ error of 10 years to the marker layers that we used for calculating the age-depth model in OxCal v. 4.2, a Bayesian age-depth modelling approach that provides posterior age uncertainties. For sedimentary macroscopic charcoal analysis, 1 cm3 of wet sediment was dissolved in water, sieved through a 150-µm mesh. Under a stereomicroscope, macroscopic charcoal of three size classes (150-300, 300-500, and ≥500 µm) was counted continuously throughout the core. To estimate a proxy error that combines sampling, preparation and macrocharcoal counting uncertainties, we continuously sampled short core JC11-K2 between 35-55 cm core depth (n = 20), i.e., interval 1840-1875 CE, that could be linked to core JC11-K5 by four marker layers as determined from varve counting. Samples were processed in the same way as for JC11-K5. The numbers of absolute particles cm-³ were compared with the JC11-K5 samples of the same time interval (n = 31) to determine an overall mean relative standard deviation of 0.8 % of each sample. The topmost 75 samples (1780-2010 CE) were also analyzed for monosaccharide anhydrides (MAs) (n = 75, 1780-2011 CE): 125-250 mg dry sediment were extracted with a DIONEX Accelerated Solvent Extractor (ASE 200, 100 °C, 7.6×106 Pa) using a 9:1 solvent mixture of dichloromethane (DCM):methanol (MeOH). As an internal standard, 2.5-5 ng deuterated levoglucosan (dLVG) was added. The total lipid extracts were separated on an unactivated SiO2 gel column (Merck Si60, grade 7754) using sequential elution with DCM:MeOH (9:1) and DCM:MeOH (1:1). The 1:1 fractions were re-dissolved in 95:5 acetonitrile:H2O and filtered using a 0.45 µm polytetrafluoroethylene filter before analysis. The MAs were analyzed by ultra-high pressure liquid chromatography-high resolution mass spectrometry. Authentic standards for LVG, GAL and MAN were obtained from Sigma Aldrich, and that for dLVG (C6H3D7O5) from Cambridge Isotope Laboratories, Inc. Integrations were performed on mass chromatograms within 3 ppm mass accuracy. Concentrations were corrected for relative response factors to dLVG of 0.997, 0.822, and 2.137 for LVG, MAN, and GAL, respectively. Instrumental (standard) errors for LVG, MAN, and GAL were 4 ± 3, 14 ± 15, and 28 ± 38% (1σ), respectively.

Description: Processed monosaccharide anhydrides records based on the raw data of sediment core JC11-K5 of Lake Czechowskie, N Poland using a robust Monte Carlo based approach that includes age and proxy measurement uncertainties in equally spaced time windows. For details and code see Dietze et al. (2019).

Description: Processed charcoal records based on the raw data of sediment core JC11-K5 of Lake Czechowskie, N Poland using a robust Monte Carlo based approach that includes age and proxy measurement uncertainties in equally spaced time windows. For details and code see Dietze et al. (2019).

Description: JC11-K5 was dated by correlating ten macroscopically visible layers with counted annual layer sequences of adjacent cores and tephra shards related to the Askja eruption in 1875 CE. As a conservative estimate, we assigned a 2σ error of 10 years to the marker layers that we used for calculating the age-depth model in OxCal v. 4.2, a Bayesian age-depth modelling approach that provides posterior age uncertainties.

Description: For sedimentary macroscopic charcoal analysis, 1 cm3 of wet sediment was dissolved in water, sieved through a 150-µm mesh. Under a stereomicroscope, macroscopic charcoal of three size classes (150-300, 300-500, and ≥500 µm) was counted continuously throughout the core. To estimate a proxy error that combines sampling, preparation and macrocharcoal counting uncertainties, we continuously sampled short core JC11-K2 between 35-55 cm core depth (n = 20), i.e., interval 1840-1875 CE, that could be linked to core JC11-K5 by four marker layers as determined from varve counting. Samples were processed in the same way as for JC11-K5. The numbers of absolute particles cm-³ were compared with the JC11-K5 samples of the same time interval (n = 31) to determine an overall mean relative standard deviation of 0.8 % of each sample. The topmost 75 samples (1780-2010 CE) were also analyzed for monosaccharide anhydrides (MAs) (n = 75, 1780-2011 CE): 125-250 mg dry sediment were extracted with a DIONEX Accelerated Solvent Extractor (ASE 200, 100 °C, 7.6×106 Pa) using a 9:1 solvent mixture of dichloromethane (DCM):methanol (MeOH). As an internal standard, 2.5-5 ng deuterated levoglucosan (dLVG) was added. The total lipid extracts were separated on an unactivated SiO2 gel column (Merck Si60, grade 7754) using sequential elution with DCM:MeOH (9:1) and DCM:MeOH (1:1). The 1:1 fractions were re-dissolved in 95:5 acetonitrile:H2O and filtered using a 0.45 µm polytetrafluoroethylene filter before analysis. The MAs were analyzed by ultra-high pressure liquid chromatography-high resolution mass spectrometry using a method adapted from earlier HPLC-ESI/MS2 methods (Hopmans et al., 2013). Authentic standards for LVG, GAL and MAN were obtained from Sigma Aldrich, and that for dLVG (C6H3D7O5) from Cambridge Isotope Laboratories, Inc. Integrations were performed on mass chromatograms within 3 ppm mass accuracy. Concentrations were corrected for relative response factors to dLVG of 0.997, 0.822, and 2.137 for LVG, MAN, and GAL, respectively. Instrumental (standard) errors for LVG, MAN, and GAL were 4 ± 3, 14 ± 15, and 28 ± 38% (1σ), respectively.