ALBERT

Description: Ocean deoxygenation is a rising threat to marine ecosystems and food resources under present climate warming conditions. Organic-rich sapropel layers deposited in the Mediterranean Sea provide a natural laboratory to study the processes that have controlled the changes in seawater oxygen levels in the recent geological past. Our study is based on three sediment cores spanning the last 10 thousand years (10 kyr BP) and located on a bathymetric transect offshore the western distributaries of the Nile delta. These cores are partly to continuously laminated in the sections recording sapropel S1, which is indicative of bottom-water anoxia above the western Nile deep-sea fan. We used a combination of microfacies analyses and inorganic and organic geochemical measurements to reconstruct changes in oxygenation conditions at seasonal to millennial time-scales. The regular alternations of detrital, biogenic and chemogenic sublayers in the laminated sequences are interpreted in terms of seasonal changes. Our microfacies analyses reveal distinct summer floods and subsequent plankton blooms preceding the deposition of inorganic carbonates formed in the water-column during spring-early summer. The isotopic signature of these carbonates suggests year-round anoxic to euxinic bottom waters resulting in high levels of anaerobic remineralisation of organic matter and highlights their potential to reconstruct seawater chemistry at times when benthic fauna was absent. Synchronous changes in terrigenous input, primary productivity and past oxygenation dynamics on millennial time-scales obtained by our multi-proxy study show that runoff-driven eutrophication played a central role in driving rapid changes in oxygenation state of the entire Levantine Basin. Rapid fluctuations of oxygenation conditions in the upper 700 m water depth occurred above the Nile deep-sea fan between 10 and 6.5 ka BP while deeper cores recorded more stable anoxic conditions. These findings are further supported by other regional records and reveal time-transgressive changes in oxygenation state driven by rapid changes in primary productivity during a period of long-term deep-water stagnation.

Description: Ocean deoxygenation is a rising threat to marine ecosystems and food resources under present climate warming conditions. Organic-rich sapropel layers deposited in the Mediterranean Sea provide a natural laboratory to study the processes that have controlled the changes in seawater oxygen levels in the recent geological past. Our study is based on three sediment cores spanning the last 10 thousand years (10 kyr BP) and located on a bathymetric transect offshore the western distributaries of the Nile delta. These cores are partly to continuously laminated in the sections recording sapropel S1, which is indicative of bottom-water anoxia above the western Nile deep-sea fan. We used a combination of microfacies analyses and inorganic and organic geochemical measurements to reconstruct changes in oxygenation conditions at seasonal to millennial time-scales. The regular alternations of detrital, biogenic and chemogenic sublayers in the laminated sequences are interpreted in terms of seasonal changes. Our microfacies analyses reveal distinct summer floods and subsequent plankton blooms preceding the deposition of inorganic carbonates formed in the water-column during spring-early summer. The isotopic signature of these carbonates suggests year-round anoxic to euxinic bottom waters resulting in high levels of anaerobic remineralisation of organic matter and highlights their potential to reconstruct seawater chemistry at times when benthic fauna was absent. Synchronous changes in terrigenous input, primary productivity and past oxygenation dynamics on millennial time-scales obtained by our multi-proxy study show that runoff-driven eutrophication played a central role in driving rapid changes in oxygenation state of the entire Levantine Basin. Rapid fluctuations of oxygenation conditions in the upper 700 m water depth occurred above the Nile deep-sea fan between 10 and 6.5 ka BP while deeper cores recorded more stable anoxic conditions. These findings are further supported by other regional records and reveal time-transgressive changes in oxygenation state driven by rapid changes in primary productivity during a period of long-term deep-water stagnation.

Description: Ocean deoxygenation is a rising threat to marine ecosystems and food resources under present climate warming conditions. Organic-rich sapropel layers deposited in the Mediterranean Sea provide a natural laboratory to study the processes that have controlled the changes in seawater oxygen levels in the recent geological past. Our study is based on three sediment cores spanning the last 10 thousand years (10 kyr BP) and located on a bathymetric transect offshore the western distributaries of the Nile delta. These cores are partly to continuously laminated in the sections recording sapropel S1, which is indicative of bottom-water anoxia above the western Nile deep-sea fan. We used a combination of microfacies analyses and inorganic and organic geochemical measurements to reconstruct changes in oxygenation conditions at seasonal to millennial time-scales. The regular alternations of detrital, biogenic and chemogenic sublayers in the laminated sequences are interpreted in terms of seasonal changes. Our microfacies analyses reveal distinct summer floods and subsequent plankton blooms preceding the deposition of inorganic carbonates formed in the water-column during spring-early summer. The isotopic signature of these carbonates suggests year-round anoxic to euxinic bottom waters resulting in high levels of anaerobic remineralisation of organic matter and highlights their potential to reconstruct seawater chemistry at times when benthic fauna was absent. Synchronous changes in terrigenous input, primary productivity and past oxygenation dynamics on millennial time-scales obtained by our multi-proxy study show that runoff-driven eutrophication played a central role in driving rapid changes in oxygenation state of the entire Levantine Basin. Rapid fluctuations of oxygenation conditions in the upper 700 m water depth occurred above the Nile deep-sea fan between 10 and 6.5 ka BP while deeper cores recorded more stable anoxic conditions. These findings are further supported by other regional records and reveal time-transgressive changes in oxygenation state driven by rapid changes in primary productivity during a period of long-term deep-water stagnation.

Description: Ocean deoxygenation is a rising threat to marine ecosystems and food resources under present climate warming conditions. Organic-rich sapropel layers deposited in the Mediterranean Sea provide a natural laboratory to study the processes that have controlled the changes in seawater oxygen levels in the recent geological past. Our study is based on three sediment cores spanning the last 10 thousand years (10 kyr BP) and located on a bathymetric transect offshore the western distributaries of the Nile delta. These cores are partly to continuously laminated in the sections recording sapropel S1, which is indicative of bottom-water anoxia above the western Nile deep-sea fan. We used a combination of microfacies analyses and inorganic and organic geochemical measurements to reconstruct changes in oxygenation conditions at seasonal to millennial time-scales. The regular alternations of detrital, biogenic and chemogenic sublayers in the laminated sequences are interpreted in terms of seasonal changes. Our microfacies analyses reveal distinct summer floods and subsequent plankton blooms preceding the deposition of inorganic carbonates formed in the water-column during spring-early summer. The isotopic signature of these carbonates suggests year-round anoxic to euxinic bottom waters resulting in high levels of anaerobic remineralisation of organic matter and highlights their potential to reconstruct seawater chemistry at times when benthic fauna was absent. Synchronous changes in terrigenous input, primary productivity and past oxygenation dynamics on millennial time-scales obtained by our multi-proxy study show that runoff-driven eutrophication played a central role in driving rapid changes in oxygenation state of the entire Levantine Basin. Rapid fluctuations of oxygenation conditions in the upper 700 m water depth occurred above the Nile deep-sea fan between 10 and 6.5 ka BP while deeper cores recorded more stable anoxic conditions. These findings are further supported by other regional records and reveal time-transgressive changes in oxygenation state driven by rapid changes in primary productivity during a period of long-term deep-water stagnation.

Description: Ocean deoxygenation is a rising threat to marine ecosystems and food resources under present climate warming conditions. Organic-rich sapropel layers deposited in the Mediterranean Sea provide a natural laboratory to study the processes that have controlled the changes in seawater oxygen levels in the recent geological past. Our study is based on three sediment cores spanning the last 10 thousand years (10 kyr BP) and located on a bathymetric transect offshore the western distributaries of the Nile delta. These cores are partly to continuously laminated in the sections recording sapropel S1, which is indicative of bottom-water anoxia above the western Nile deep-sea fan. We used a combination of microfacies analyses and inorganic and organic geochemical measurements to reconstruct changes in oxygenation conditions at seasonal to millennial time-scales. The regular alternations of detrital, biogenic and chemogenic sublayers in the laminated sequences are interpreted in terms of seasonal changes. Our microfacies analyses reveal distinct summer floods and subsequent plankton blooms preceding the deposition of inorganic carbonates formed in the water-column during spring-early summer. The isotopic signature of these carbonates suggests year-round anoxic to euxinic bottom waters resulting in high levels of anaerobic remineralisation of organic matter and highlights their potential to reconstruct seawater chemistry at times when benthic fauna was absent. Synchronous changes in terrigenous input, primary productivity and past oxygenation dynamics on millennial time-scales obtained by our multi-proxy study show that runoff-driven eutrophication played a central role in driving rapid changes in oxygenation state of the entire Levantine Basin. Rapid fluctuations of oxygenation conditions in the upper 700 m water depth occurred above the Nile deep-sea fan between 10 and 6.5 ka BP while deeper cores recorded more stable anoxic conditions. These findings are further supported by other regional records and reveal time-transgressive changes in oxygenation state driven by rapid changes in primary productivity during a period of long-term deep-water stagnation.

Description: Ocean deoxygenation is a rising threat to marine ecosystems and food resources under present climate warming conditions. Organic-rich sapropel layers deposited in the Mediterranean Sea provide a natural laboratory to study the processes that have controlled the changes in seawater oxygen levels in the recent geological past. Our study is based on three sediment cores spanning the last 10 thousand years (10 kyr BP) and located on a bathymetric transect offshore the western distributaries of the Nile delta. These cores are partly to continuously laminated in the sections recording sapropel S1, which is indicative of bottom-water anoxia above the western Nile deep-sea fan. We used a combination of microfacies analyses and inorganic and organic geochemical measurements to reconstruct changes in oxygenation conditions at seasonal to millennial time-scales. The regular alternations of detrital, biogenic and chemogenic sublayers in the laminated sequences are interpreted in terms of seasonal changes. Our microfacies analyses reveal distinct summer floods and subsequent plankton blooms preceding the deposition of inorganic carbonates formed in the water-column during spring-early summer. The isotopic signature of these carbonates suggests year-round anoxic to euxinic bottom waters resulting in high levels of anaerobic remineralisation of organic matter and highlights their potential to reconstruct seawater chemistry at times when benthic fauna was absent. Synchronous changes in terrigenous input, primary productivity and past oxygenation dynamics on millennial time-scales obtained by our multi-proxy study show that runoff-driven eutrophication played a central role in driving rapid changes in oxygenation state of the entire Levantine Basin. Rapid fluctuations of oxygenation conditions in the upper 700 m water depth occurred above the Nile deep-sea fan between 10 and 6.5 ka BP while deeper cores recorded more stable anoxic conditions. These findings are further supported by other regional records and reveal time-transgressive changes in oxygenation state driven by rapid changes in primary productivity during a period of long-term deep-water stagnation.

Description: Ocean deoxygenation is a rising threat to marine ecosystems and food resources under present climate warming conditions. Organic-rich sapropel layers deposited in the Mediterranean Sea provide a natural laboratory to study the processes that have controlled the changes in seawater oxygen levels in the recent geological past. Our study is based on three sediment cores spanning the last 10 thousand years (10 kyr BP) and located on a bathymetric transect offshore the western distributaries of the Nile delta. These cores are partly to continuously laminated in the sections recording sapropel S1, which is indicative of bottom-water anoxia above the western Nile deep-sea fan. We used a combination of microfacies analyses and inorganic and organic geochemical measurements to reconstruct changes in oxygenation conditions at seasonal to millennial time-scales. The regular alternations of detrital, biogenic and chemogenic sublayers in the laminated sequences are interpreted in terms of seasonal changes. Our microfacies analyses reveal distinct summer floods and subsequent plankton blooms preceding the deposition of inorganic carbonates formed in the water-column during spring-early summer. The isotopic signature of these carbonates suggests year-round anoxic to euxinic bottom waters resulting in high levels of anaerobic remineralisation of organic matter and highlights their potential to reconstruct seawater chemistry at times when benthic fauna was absent. Synchronous changes in terrigenous input, primary productivity and past oxygenation dynamics on millennial time-scales obtained by our multi-proxy study show that runoff-driven eutrophication played a central role in driving rapid changes in oxygenation state of the entire Levantine Basin. Rapid fluctuations of oxygenation conditions in the upper 700 m water depth occurred above the Nile deep-sea fan between 10 and 6.5 ka BP while deeper cores recorded more stable anoxic conditions. These findings are further supported by other regional records and reveal time-transgressive changes in oxygenation state driven by rapid changes in primary productivity during a period of long-term deep-water stagnation.

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.