ALBERT

Description: This dataset provides first results of the ongoing search for cryptotephras in the International Continental Scientific Drilling Program (ICDP) sediment core 5017-1 retrieved from the deep northern DS basin in 2010/11. 56 samples from sediments and rock salts were collected between 89.30 and 94.09 m sediment depth below lake floor from cores 5017-1-A-43 and 5017-1-A-44, focusing on the Lateglacial time period (~15-11.4 cal. ka BP), when Lake Lisan – the precursor of the DS – shrank from its glacial high-stand to the Holocene low levels. Sampling was performed in contiguous 5 cm steps with sample volumes of 5 cm³ and excluding mass-transported deposits thicker than 5 cm. The cryptotephra glass-shard extraction protocol followed established separation procedures (Blockley et al. 2005, doi:10.1016/j.quascirev.2004.12.008), and has been further adapted to the extreme salinity and sediment recycling of the DS. Glass shards were picked using a 100 μm-diameter gas-chromatography syringe attached to a micromanipulator (Lane et al. 2014, doi:10.1016/j.jas.2013.10.033), embedded in Araldite 2020 epoxy resin and ground and polished for electron probe microanalyses (EPMA). Major-element composition of individual glass shards was measured using a JEOL JXA-8230 electron microprobe at GFZ Potsdam, Germany (15 kV, 5-10 nA, 5-10 µm beam size). Instrumental calibration used natural mineral standards and the precision and accuracy of measurements during analytical runs were monitored using the glass standards Lipari obsidian (Hunt & Hill 1996, doi:10.1016/1040-6182(95)00088-7; Kuehn et al. 2011,doi:10.1016/j.quaint.2011.08.022) and MPI-Ding glasses ATHO-G, StHs-6-80-G and GOR-132-G (Jochum et al. 2006, doi:10.1029/2005GC001060). From six glass samples at least 10 glass shards per sample were measured by EPMA and for three samples replicate measurements on different glass shards were performed. After removal of glass geochemical measurements with totals 〈90%, 102 glass shard measurements remain in total. In general, cryptotephra is abundant in the Dead Sea record (up to ~100 shards per cm³), but often glasses are physically and/or chemically altered. The glass shard measurements reveal a heterogeneous geochemical composition, with mainly rhyolitic and some trachytic glasses potentially sourced from Italian, Aegean and Anatolian volcanoes. These first results demonstrate the great potential of crypto-tephrochronology in the DS record for improving its chronology and connecting the Levantine region to the Mediterranean tephra framework.

Description: To revise the chronology for the Lake Gościąż record, sediment cores were retrieved during two field campaigns in 2015 and 2018. Four overlapping sections were collected using a UWITEC Piston Corer (Ø 90 mm) in the deepest part of Lake Gościąż, Poland (52.583022 N, 19.339946 E). The chronology was obtained by triple varve counting on petrographic thin sections that was complemented by 137Cs measurements and 14C AMS dating of terrestrial plant remains. Additionally, part of the chronology between 520-758 cm was obtained through age-depth modelling. Pollen analysis was performed for seventy one samples, prepared according to standard procedure, and analyzed in three intervals: i) from 1859.9 cm to 1874.4 cm with 2 cm resolution, ii) from 1880.2 cm to 1896.7 cm with 1-2 cm resolution and iii) from 1741.4 cm to 1798.4 cm with 0.5-3 cm resolution. The record is mostly varved and the bottom of the composite profile coincides with the onset of lacustrine sedimentation in the late Allerød at 12,834 +134/-233 varve yrs BP.

Description: 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. Chironomidae head capsules (hc) were utilized to reconstruct the mean July air temperature from the late Allerød to the early Preboreal in Lake Gościąż (central Poland). Sample resolution ranges from 0.5 to 6 cm. Two different training sets were used for the reconstruction - the Swiss-Norwegian-Polish Training Set (SNP TS) (Kotrys et al. 2020) and the East European TS (EE TS) (Luoto et al. 2019). Both use the Weighted Averaging-Partial Least Squares transfer function (WA-PLS).The dataset incorporates the composite depth and age [BP] for the sample midpoint, as well as for both training sets, respectively, the chironomid-inferred mean July air temperature, the standard error and the squared chi-square distance between the fossil sample and its closest modern analogue in the respective training set.

Description: To revise the chronology for the Lake Gościąż record, sediment cores were retrieved during two field campaigns in 2015 and 2018. Four overlapping sections were collected using a UWITEC Piston Corer (Ø 90 mm) in the deepest part of Lake Gościąż, Poland (52.583022 N, 19.339946 E). The chronology was obtained by triple varve counting on petrographic thin sections that was complemented by 137Cs measurements and 14C AMS dating of terrestrial plant remains. Additionally, part of the chronology between 520-758 cm was obtained through age-depth modelling. Pollen analysis was performed for seventy one samples, prepared according to standard procedure, and analyzed in three intervals: i) from 1859.9 cm to 1874.4 cm with 2 cm resolution, ii) from 1880.2 cm to 1896.7 cm with 1-2 cm resolution and iii) from 1741.4 cm to 1798.4 cm with 0.5-3 cm resolution. The record is mostly varved and the bottom of the composite profile coincides with the onset of lacustrine sedimentation in the late Allerød at 12,834 +134/-233 varve yrs BP.

Description: To revise the chronology for the Lake Gościąż record, sediment cores were retrieved during two field campaigns in 2015 and 2018. Four overlapping sections were collected using a UWITEC Piston Corer (Ø 90 mm) in the deepest part of Lake Gościąż, Poland (52.583022 N, 19.339946 E). The chronology was obtained by triple varve counting on petrographic thin sections that was complemented by 137Cs measurements and 14C AMS dating of terrestrial plant remains. Additionally, part of the chronology between 520-758 cm was obtained through age-depth modelling. Pollen analysis was performed for seventy one samples, prepared according to standard procedure, and analyzed in three intervals: i) from 1859.9 cm to 1874.4 cm with 2 cm resolution, ii) from 1880.2 cm to 1896.7 cm with 1-2 cm resolution and iii) from 1741.4 cm to 1798.4 cm with 0.5-3 cm resolution. The record is mostly varved and the bottom of the composite profile coincides with the onset of lacustrine sedimentation in the late Allerød at 12,834 +134/-233 varve yrs BP.

Description: 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.

Description: This dataset provides first results of the ongoing search for cryptotephras in the International Continental Scientific Drilling Program (ICDP) sediment core 5017-1 retrieved from the deep northern Dead Sea (DS) basin in 2010/11. 56 samples from sediments and rock salts were collected between 89.30 and 94.09 m sediment depth below lake floor from cores 5017-1-A-43 and 5017-1-A-44, focusing on the Lateglacial time period (~15-11.4 cal. ka BP), when Lake Lisan – the precursor of the DS – shrank from its glacial high-stand to the Holocene low levels. Sampling was performed in contiguous 5 cm steps with sample volumes of 5 cm³ and excluding mass-transported deposits thicker than 5 cm. The cryptotephra glass-shard extraction protocol followed established separation procedures (Blockley et al. 2005, doi:10.1016/j.quascirev.2004.12.008), and has been further adapted to the extreme salinity and sediment recycling of the DS. Glass shards were picked using a 100 μm-diameter gas-chromatography syringe attached to a micromanipulator (Lane et al. 2014, doi:10.1016/j.jas.2013.10.033), embedded in Araldite 2020 epoxy resin and ground and polished for electron probe microanalyses (EPMA). Major-element composition of individual glass shards was measured using a JEOL JXA-8230 electron microprobe at GFZ Potsdam, Germany (15 kV, 5-10 nA, 5-10 µm beam size). Instrumental calibration used natural mineral standards and analytical runs were monitored using glass standards (see second dataset). From six glass samples at least 10 glass shards per sample were measured by EPMA and for three samples replicate measurements on different glass shards were performed. After removal of glass geochemical measurements with totals 〈90%, 102 glass shard measurements remain in total. In general, cryptotephra is abundant in the Dead Sea record (up to ~100 shards per cm³), but often glasses are physically and/or chemically altered. The glass shard measurements reveal a heterogeneous geochemical composition, with mainly rhyolitic and some trachytic glasses potentially sourced from Italian, Aegean and Anatolian volcanoes. These first results demonstrate the great potential of crypto-tephrochronology in the DS record for improving its chronology and connecting the Levantine region to the Mediterranean tephra framework.

Description: This dataset provides the data for the four glass standards used for monitoring of the precision and accuracy of electron probe microanalyses (EPMA) during analytical runs of cryptotephra glass-shards in the International Continental Scientific Drilling Program (ICDP) sediment core 5017-1 (see first dataset). For each EPMA run, all four glass standards were measured. The major-element composition of the glass standards was measured using a JEOL JXA-8230 electron microprobe at GFZ Potsdam, Germany (15 kV, 5-10 nA, 5-10 µm beam size). Instrumental calibration used natural mineral standards. Glass standards were Lipari obsidian (Hunt & Hill 1996, doi:10.1016/1040-6182(95)00088-7; Kuehn et al. 2011, doi:10.1016/j.quaint.2011.08.022) and MPI-Ding glasses ATHO-G, StHs-6-80-G and GOR-132-G (Jochum et al. 2006, doi:10.1029/2005GC001060).

Description: 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. Our varve chronology is the lowest part of a new floating varve chronology established for Lake Gościąż (central Poland) that has been anchored to the absolute time scale through radiocarbon dating and age modelling (Bonk et al., in press). The here presented varve chronology reaches from the onset of lacustrine sedimentation in the late Allerød until the early Preboreal. Uncertainties for the absolute ages are derived from radiocarbon age modelling and varve counting. The internal varve counting uncertainty for the observed time interval is generally low (+14/-22) due to the mostly excellent varve preservation. Microfacies analyses, including varve counting and measurements of varve and sublayer thickness, have been performed on overlapping large-scale thin sections under an Axioplan 2 and Axiolab pol imaging microscope at magnifications of 50-400x. Thin sections have been prepared from 10 cm long freeze-dried and resin impregnated sediment slices (Brauer & Casanova 2001; doi:10.1023/A:1008136029735). The dataset incorporates the composite depth, age [BP] and age uncertainties [BP] for the varve bottom, the total varve thickness, selected sublayer thicknesses, detrital sublayer occurrence, the different varve types and the varve quality index (VQI).

Description: Varved lake sediments provide long climatic records with high temporal resolution and low associated age uncertainty. Robust and detailed comparison of well-dated and annually laminated sediment records is crucial for reconstructing abrupt and regionally time-transgressive changes as well as validation of spatial and temporal trajectories of past climatic changes. The VARved sediments DAtabase (VARDA) presented here is the first data compilation for varve chronologies and associated palaeoclimatic proxy records. The current version 1.0 allows detailed comparison of published varve records from 95 lakes. VARDA is freely accessible and was created to assess outputs from climate models with high-resolution terrestrial palaeoclimatic proxies. VARDA additionally provides a technical environment that enables to explore the database of varved lake sediments using a connected data-model and can generate a state-of-the-art graphic representation of multi-site comparison. This allows to reassess existing chronologies and tephra events to synchronize and compare even distant varved lake records. Furthermore, the present version of VARDA permits to explore varve thickness data. In this paper, we report in detail on the data mining and compilation strategies for the identification of varved lakes and assimilation of high-resolution chronologies as well as the technical infrastructure of the database. Additional paleoclimate proxy data will be provided in forthcoming updates. The VARDA graph-database and user interface can be accessed online at https://varve.gfz-potsdam.de, all datasets of version 1.0 are available at http://doi.org/10.5880/GFZ.4.3.2019.003 (Ramisch et al., 2019).