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  • Open Access English
    Authors: 
    Beddow, Helen M; Liebrand, Diederik; Wilson, Douglas S; Hilgen, Frederik J; Sluijs, Appy; Wade, Bridget S; Lourens, Lucas Joost;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: EC | EARTHSEQUENCING (617462), EC | ERAS (293741), NWO | Evolution of astronomical... (2300157723)

    Astronomical tuning of sediment sequences requires both unambiguous cycle-pattern recognition in climate proxy records and astronomical solutions, and independent information about the phase relationship between these two. Here we present two different astronomically tuned age models for the Oligocene-Miocene Transition (OMT) from Integrated Ocean Drilling Program Site U1334 (equatorial Pacific Ocean) to assess the effect tuning has on astronomically calibrated ages and the geologic time scale. These alternative age models (from ~22 to ~24 Ma) are based on different tunings between proxy records and eccentricity: the first age model is based on an aligning CaCO3 weight (wt%) to Earth's orbital eccentricity, the second age model is based on a direct age calibration of benthic foraminiferal stable carbon isotope ratios (d13C) to eccentricity. To independently test which tuned age model and associated tuning assumptions is in best agreement with independent ages based on tectonic plate-pair spreading rates, we assign our tuned ages to the magnetostratigraphic reversals identified in deep-marine magnetic anomaly profiles. Subsequently, we compute tectonic plate-pair spreading rates based on the tuned ages. The resultant, alternative spreading rate histories indicate that the CaCO3 tuned age model is most consistent with a conservative assumption of constant, or linearly changing, spreading rates. The CaCO3 tuned age model thus provides robust ages and durations for polarity chrons C6Bn.1n-C6Cn.1r, which are not based on astronomical tuning in the latest iteration of the Geologic Time Scale. Furthermore, it provides independent evidence that the relatively large (several 10,000 years) time lags documented in the benthic foraminiferal isotope records relative to orbital eccentricity, constitute a real feature of the Oligocene-Miocene climate system and carbon cycle. The age constraints from Site U1334 thus provide independent evidence that the delayed responses of the Oligocene-Miocene climate-cryosphere system and carbon cycle resulted from highly nonlinear feedbacks to astronomical forcing.

  • English
    Authors: 
    Sluijs, Appy; Bijl, Peter K; Schouten, Stefan; R��hl, Ursula; Reichart, Gert-Jan; Brinkhuis, Henk;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: NWO | Biotic, climatic and geoc... (2300137050), EC | DINOPRO (259627)

    A brief (~150 kyr) period of widespread global average surface warming marks the transition between the Paleocene and Eocene epochs, ~56 million years ago. This so-called "Paleocene-Eocene thermal maximum" (PETM) is associated with the massive injection of 13C-depleted carbon, reflected in a negative carbon isotope excursion (CIE). Biotic responses include a global abundance peak (acme) of the subtropical dinoflagellate Apectodinium. Here we identify the PETM in a marine sedimentary sequence deposited on the East Tasman Plateau at Ocean Drilling Program (ODP) Site 1172 and show, based on the organic paleothermometer TEX86, that southwest Pacific sea surface temperatures increased from ~26 ��C to ~33��C during the PETM. Such temperatures before, during and after the PETM are >10 ��C warmer than predicted by paleoclimate model simulations for this latitude. In part, this discrepancy may be explained by potential seasonal biases in the TEX86 proxy in polar oceans. Additionally, the data suggest that not only Arctic, but also Antarctic temperatures may be underestimated in simulations of ancient greenhouse climates by current generation fully coupled climate models. An early influx of abundant Apectodinium confirms that environmental change preceded the CIE on a global scale. Organic dinoflagellate cyst assemblages suggest a local decrease in the amount of river run off reaching the core site during the PETM, possibly in concert with eustatic rise. Moreover, the assemblages suggest changes in seasonality of the regional hydrological system and storm activity. Finally, significant variation in dinoflagellate cyst assemblages during the PETM indicates that southwest Pacific climates varied significantly over time scales of 103 - 104 years during this event, a finding comparable to similar studies of PETM successions from the New Jersey Shelf.

  • English
    Authors: 
    Frieling, Joost; Reichart, Gert-Jan; Middelburg, Jack J; R��hl, Ursula; Westerhold, Thomas; Bohaty, Steven M; Sluijs, Appy;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: NWO | A sensitive ultra high pr... (2300165371), EC | DINOPRO (259627)

    The Paleocene - Eocene Thermal Maximum (PETM; 56 Ma) was a phase of rapid global warming associated with massive carbon input into the ocean-atmosphere system from a 13C-depleted reservoir. Many mid- and high-latitude sections have been studied and document changes in salinity, hydrology and sedimentation, deoxygenation, biotic overturning and migrations, but detailed records from tropical regions are lacking. Here, we study the PETM at Ocean Drilling Program (ODP) Site 959 in the equatorial Atlantic using a range of organic and inorganic proxies and couple these with dinoflagellate cyst (dinocyst) assemblage analysis. The PETM at Site 959 was previously found to be marked by a ~3.8 per mil negative carbon isotope excursion (CIE), and a ~4 ��C surface ocean warming from the uppermost Paleocene to peak PETM, of which ~1 ��C occurs before the onset of the CIE. We record upper Paleocene dinocyst assemblages that are similar to PETM assemblages as found in extra-tropical regions, confirming poleward migrations of ecosystems during the PETM. The early stages of the PETM are marked by a typical acme of the tropical genus Apectodinium, which reaches abundances of up to 95 %. Subsequently, dinocyst abundances diminish greatly, as do carbonate and pyritized silicate microfossils. The combined paleoenvironmental information from Site 959 and a close by shelf site in Nigeria implies the general absence of eukaryotic surface-dwelling microplankton during peak PETM warmth is most likely caused by heat stress. Crucially, abundant organic benthic foraminiferal linings imply sustained export production, likely driven by prokaryotes. In sharp contrast, the recovery of the CIE yields rapid (<<10 kyr) fluctuations in the abundance of several dinocyst groups, suggesting extreme ecosystem and environmental variability.

  • Open Access English
    Authors: 
    Salabarnada, Ariadna; Escutia, Carlota; Röhl, Ursula; Nelson, C Hans; McKay, Robert M; Jiménez-Espejo, Francisco Jose; Bijl, Peter K; Hartman, Julian D; Ikehara, Minoru; Strother, Stephanie L; +6 more
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: NWO | Reconstructing the the ev... (2300166023), NWO | The Dawn of a Greenhouse ... (2300180216)

    Antarctic ice sheet and Southern Ocean paleoceanographic configurations during the late Oligocene are not well resolved. They are however important to understand the influence of high-latitude Southern Hemisphere feedbacks on global climate under CO2 scenarios (between 400 and 750 ppm) projected by the IPCC for this century, assuming unabated CO2 emissions. Sediments recovered by the Integrated Ocean Drilling Program (IODP) at Site U1356, offshore of the Wilkes Land margin in East Antarctica, provide an opportunity to study ice sheet and paleoceanographic configurations during the late Oligocene (26-25 Ma). Our study, based on a combination of sediment facies analysis, magnetic susceptibility, density, and X-Ray Fluorescence geochemical data, shows that glacial and interglacial sediments are continuously reworked by bottom-currents, with maximum velocities occurring during the interglacial periods. Glacial sediments record poorly ventilated, low-oxygenation bottom water conditions, interpreted to result from a northward shift of westerly winds and surface oceanic fronts. Interglacial sediments record more oxygenated and ventilated bottom water conditions and strong current velocities, which suggests enhanced mixing of the water masses as a result of a southward shift of the Polar Front. Intervals with preserved carbonated nannofossils within some of the interglacial facies are interpreted to form under warmer paleoclimatic conditions when less corrosive warmer northern component water (e.g. North Atlantic sourced deep water) had a greater influence on the Site. Spectral analysis on the late Oligocene sediment interval show that the glacial-interglacial cyclicity and related displacements of the Southern Ocean frontal systems between 26-25 Ma were forced mainly by obliquity. The paucity of iceberg rafted debris (IRD) throughout the studied interval contrasts with earlier Oligocene and post-Miocene Climate Optimum sections from Site U1356 and with late Oligocene strata from the Ross Sea, which contain IRD and evidence for coastal glaciers and sea ice. These observations, supported by elevated sea surface paleotemperatures, the absence of sea-ice, and reconstructions of fossil pollen between 26 and 25 Ma at Site U1356, suggest that open ocean water conditions prevailed. Combined, these evidences suggest that glaciers or ice caps likely occupied the topographic highs and lowlands of the now marine Wilkes Subglacial Basin (WSB). Unlike today, the continental shelf was not over-deepened and thus ice sheets in the WSB were likely land-based and marine-based ice sheet expansion was likely limited to coastal regions.

  • Open Access
    Authors: 
    Agnieszka Płonka;
    Publisher: Zenodo
    Project: NWO | Full waveform inversion f... (2300172344)

    This dataset should provide complete synthetic seismograms and software (python tools for random media generation, signal comparison and histogram stacking) that were used in the publication: Płonka, A., Blom, N., and Fichtner, A.: The imprint of crustal density heterogeneities on regional seismic wave propagation, Solid Earth, 7, 1591-1608, doi:10.5194/se-7-1591-2016, 2016.

  • Authors: 
    Pierik, Harm Jan; Rowin J Van Lanen; Gouw-Bouman, Marjolein TIJ; Groenewoudt, Bert J; Wallinga, Jakob; Hoek, Wim Z;
    Publisher: SAGE Journals
    Project: NWO | The Dark Age of the Lowla... (2300172486)

    Supplemental material, Appendix_A_and_B for Controls on late-Holocene drift-sand dynamics: The dominant role of human pressure in the Netherlands by Harm Jan Pierik, Rowin J van Lanen, Marjolein TIJ Gouw-Bouman, Bert J Groenewoudt, Jakob Wallinga and Wim Z Hoek in The Holocene

  • English
    Authors: 
    Frieling, Joost; Huurdeman, Emiel P; Rem, Charlotte C M; Donders, Timme H; Pross, J��rg; Bohaty, Steven M; Holdgate, Guy R; Gallagher, Stephen John; McGowran, Brian; Bijl, Peter K;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: NWO | The Dawn of a Greenhouse ... (2300180216)

    Detailed, stratigraphically well-constrained environmental reconstructions are available for Paleocene and Eocene strata at a range of sites in the southwest Pacific Ocean (New Zealand and East Tasman Plateau; ETP) and Integrated Ocean Discovery Program (IODP) Site U1356 in the south of the Australo-Antarctic Gulf (AAG). These reconstructions have revealed a large discrepancy between temperature proxy data and climate models in this region, suggesting a crucial error in model, proxy data or both. To resolve the origin of this discrepancy, detailed reconstructions are needed from both sides of the Tasmanian Gateway. Paleocene-Eocene sedimentary archives from the west of the Tasmanian Gateway have unfortunately remained scarce (only IODP Site U1356), and no well-dated successions are available for the northern sector of the AAG. Here we present new stratigraphic data for upper Paleocene and lower Eocene strata from the Otway Basin, southeast Australia, on the (north)west side of the Tasmanian Gateway. We analyzed sediments recovered from exploration drilling (Latrobe-1 drill core) and outcrop sampling (Point Margaret) and performed high-resolution carbon isotope geochemistry of bulk organic matter and dinoflagellate cyst (dinocyst) and pollen biostratigraphy on sediments from the regional lithostratigraphic units, including the Pebble Point Formation, Pember Mudstone and Dilwyn Formation. Pollen and dinocyst assemblages are assigned to previously established Australian pollen and dinocyst zonations and tied to available zonations for the SW Pacific. Based on our dinocyst stratigraphy and previously published planktic foraminifer biostratigraphy, the Pebble Point Formation at Point Margaret is dated to the latest Paleocene. The globally synchronous negative carbon isotope excursion that marks the Paleocene-Eocene boundary is identified within the top part of the Pember Mudstone in the Latrobe-1 borehole and at Point Margaret. However, the high abundances of the dinocyst Apectodinium prior to this negative carbon isotope excursion prohibit a direct correlation of this regional bio-event with the quasi-global Apectodinium acme at the Paleocene-Eocene Thermal Maximum (PETM; 56 Ma). Therefore, the first occurrence of the pollen species Spinizonocolpites prominatus and the dinocyst species Florentinia reichartii are here designated as regional markers for the PETM. In the Latrobe-1 drill core, dinocyst biostratigraphy further indicates that the early Eocene (~56-51 Ma) sediments are truncated by a ~10 Myr long hiatus overlain by middle Eocene (~40 Ma) strata. These sedimentary archives from southeast Australia may prove key in resolving the model-data discrepancy in this region, and the new stratigraphic data presented here allow for detailed comparisons between paleoclimate records on both sides of the Tasmanian Gateway.

  • Open Access
    Authors: 
    Vlietstra, Wytze; Vos, Rein; Sijbers, Anneke; Mulligen, Erik Van; Kors, Jan;
    Publisher: figshare
    Project: NWO | ODEX4all Open Discovery a... (2300182466), NWO | XCiDE: Crossing the Combu... (2300153186)

    Performance for different ratios between the positive and the negative cases in the training set. This file shows the performance on a balanced test set as a function of the ratio of positive and negative cases in the training set. (XLSX 14 kb)

  • Open Access English
    Authors: 
    Lauretano, Vittoria; Littler, Kate; Polling, M; Zachos, James C; Lourens, Lucas Joost;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: NWO | Evolution of astronomical... (2300157723)

    Recent studies have shown that the Early Eocene Climatic Optimum (EECO) was preceded by a series of short-lived global warming events, known as hyperthermals. Here we present high-resolution benthic stable carbon and oxygen isotope records from ODP Sites 1262 and 1263 (Walvis Ridge, SE Atlantic) between ~54 and ~52 million years ago, tightly constraining the character, timing, and magnitude of six prominent hyperthermal events. These events, which include Eocene Thermal Maximum (ETM) 2 and 3, are studied in relation to orbital forcing and long-term trends. Our findings reveal an almost linear relationship between d13C and d18O for all these hyperthermals, indicating that the eccentricity-paced co-variance between deep-sea temperature changes and extreme perturbations in the exogenic carbon pool persisted during these events towards the onset of the EECO, in accord with previous observations for the Paleocene Eocene Thermal Maximum (PETM) and ETM2. The covariance of d13C and d18O during H2 and I2, which are the second pulses of the "paired" hyperthermal events ETM2-H2 and I1-I2, deviates with respect to the other events. We hypothesize that this could relate to a relatively higher contribution of an isotopically heavier source of carbon, such as peat or permafrost, and/or to climate feedbacks/local changes in circulation. Finally, the d18O records of the two sites show a systematic offset with on average 0.2 per mil heavier values for the shallower Site 1263, which we link to a slightly heavier isotopic composition of the intermediate water mass reaching the northeastern flank of the Walvis Ridge compared to that of the deeper northwestern water mass at Site 1262.

  • Open Access English
    Authors: 
    Gürer, Derya; van Hinsbergen, Douwe J J; Özkaptan, Murat; Creton, Iverna; Koymans, Mathijs R; Cascella, Antonio; Langereis, Cornelis G;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: NWO | Subduction Initiation rec... (2300172509), EC | SINK (306810)

    To quantitatively reconstruct the kinematic evolution of Central and Eastern Anatolia within the framework of Neotethyan subduction accommodating Africa-Eurasia convergence, we paleomagnetically assess timing and amount of vertical axis rotations across the Ulukisla and Sivas regions. We show paleomagnetic results from ~30 localities identifying a coherent rotation of a block - comprising the southern Kirsehir Block, the Ulukisla basin, the Central and Eastern Taurides, and the southern part of the Sivas basin. This block experienced a ~30° counter-clockwise vertical axis rotation since Oligocene time. Sediments in the northern Sivas region show clockwise rotations. We use the rotation patterns together with known fault zones to argue that the counter-clockwise rotating domain of south-central Turkey was bounded by the Savcili Thrust Zone and Deliler-Tecer Fault Zone in the north and by the African-Arabian trench in the south, the western boundary of which is poorly constrained and requires future study. Our new paleomagnetic constraints provide a key ingredient for future kinematic restorations of the Anatolian tectonic collage. We combine our extensive new dataset with existing data (Guerer et al., 2018, and references therein) to identify the dimension of rotating domains in Central and Eastern Anatolia, and identify structures that may have accommodated these rotations. Paleomagnetic interpretations and statistical analyses were carried out using the platform independent portal Paleomagnetism.org (Koymans et al., 2016).

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12 Research products, page 1 of 2
  • Open Access English
    Authors: 
    Beddow, Helen M; Liebrand, Diederik; Wilson, Douglas S; Hilgen, Frederik J; Sluijs, Appy; Wade, Bridget S; Lourens, Lucas Joost;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: EC | EARTHSEQUENCING (617462), EC | ERAS (293741), NWO | Evolution of astronomical... (2300157723)

    Astronomical tuning of sediment sequences requires both unambiguous cycle-pattern recognition in climate proxy records and astronomical solutions, and independent information about the phase relationship between these two. Here we present two different astronomically tuned age models for the Oligocene-Miocene Transition (OMT) from Integrated Ocean Drilling Program Site U1334 (equatorial Pacific Ocean) to assess the effect tuning has on astronomically calibrated ages and the geologic time scale. These alternative age models (from ~22 to ~24 Ma) are based on different tunings between proxy records and eccentricity: the first age model is based on an aligning CaCO3 weight (wt%) to Earth's orbital eccentricity, the second age model is based on a direct age calibration of benthic foraminiferal stable carbon isotope ratios (d13C) to eccentricity. To independently test which tuned age model and associated tuning assumptions is in best agreement with independent ages based on tectonic plate-pair spreading rates, we assign our tuned ages to the magnetostratigraphic reversals identified in deep-marine magnetic anomaly profiles. Subsequently, we compute tectonic plate-pair spreading rates based on the tuned ages. The resultant, alternative spreading rate histories indicate that the CaCO3 tuned age model is most consistent with a conservative assumption of constant, or linearly changing, spreading rates. The CaCO3 tuned age model thus provides robust ages and durations for polarity chrons C6Bn.1n-C6Cn.1r, which are not based on astronomical tuning in the latest iteration of the Geologic Time Scale. Furthermore, it provides independent evidence that the relatively large (several 10,000 years) time lags documented in the benthic foraminiferal isotope records relative to orbital eccentricity, constitute a real feature of the Oligocene-Miocene climate system and carbon cycle. The age constraints from Site U1334 thus provide independent evidence that the delayed responses of the Oligocene-Miocene climate-cryosphere system and carbon cycle resulted from highly nonlinear feedbacks to astronomical forcing.

  • English
    Authors: 
    Sluijs, Appy; Bijl, Peter K; Schouten, Stefan; R��hl, Ursula; Reichart, Gert-Jan; Brinkhuis, Henk;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: NWO | Biotic, climatic and geoc... (2300137050), EC | DINOPRO (259627)

    A brief (~150 kyr) period of widespread global average surface warming marks the transition between the Paleocene and Eocene epochs, ~56 million years ago. This so-called "Paleocene-Eocene thermal maximum" (PETM) is associated with the massive injection of 13C-depleted carbon, reflected in a negative carbon isotope excursion (CIE). Biotic responses include a global abundance peak (acme) of the subtropical dinoflagellate Apectodinium. Here we identify the PETM in a marine sedimentary sequence deposited on the East Tasman Plateau at Ocean Drilling Program (ODP) Site 1172 and show, based on the organic paleothermometer TEX86, that southwest Pacific sea surface temperatures increased from ~26 ��C to ~33��C during the PETM. Such temperatures before, during and after the PETM are >10 ��C warmer than predicted by paleoclimate model simulations for this latitude. In part, this discrepancy may be explained by potential seasonal biases in the TEX86 proxy in polar oceans. Additionally, the data suggest that not only Arctic, but also Antarctic temperatures may be underestimated in simulations of ancient greenhouse climates by current generation fully coupled climate models. An early influx of abundant Apectodinium confirms that environmental change preceded the CIE on a global scale. Organic dinoflagellate cyst assemblages suggest a local decrease in the amount of river run off reaching the core site during the PETM, possibly in concert with eustatic rise. Moreover, the assemblages suggest changes in seasonality of the regional hydrological system and storm activity. Finally, significant variation in dinoflagellate cyst assemblages during the PETM indicates that southwest Pacific climates varied significantly over time scales of 103 - 104 years during this event, a finding comparable to similar studies of PETM successions from the New Jersey Shelf.

  • English
    Authors: 
    Frieling, Joost; Reichart, Gert-Jan; Middelburg, Jack J; R��hl, Ursula; Westerhold, Thomas; Bohaty, Steven M; Sluijs, Appy;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: NWO | A sensitive ultra high pr... (2300165371), EC | DINOPRO (259627)

    The Paleocene - Eocene Thermal Maximum (PETM; 56 Ma) was a phase of rapid global warming associated with massive carbon input into the ocean-atmosphere system from a 13C-depleted reservoir. Many mid- and high-latitude sections have been studied and document changes in salinity, hydrology and sedimentation, deoxygenation, biotic overturning and migrations, but detailed records from tropical regions are lacking. Here, we study the PETM at Ocean Drilling Program (ODP) Site 959 in the equatorial Atlantic using a range of organic and inorganic proxies and couple these with dinoflagellate cyst (dinocyst) assemblage analysis. The PETM at Site 959 was previously found to be marked by a ~3.8 per mil negative carbon isotope excursion (CIE), and a ~4 ��C surface ocean warming from the uppermost Paleocene to peak PETM, of which ~1 ��C occurs before the onset of the CIE. We record upper Paleocene dinocyst assemblages that are similar to PETM assemblages as found in extra-tropical regions, confirming poleward migrations of ecosystems during the PETM. The early stages of the PETM are marked by a typical acme of the tropical genus Apectodinium, which reaches abundances of up to 95 %. Subsequently, dinocyst abundances diminish greatly, as do carbonate and pyritized silicate microfossils. The combined paleoenvironmental information from Site 959 and a close by shelf site in Nigeria implies the general absence of eukaryotic surface-dwelling microplankton during peak PETM warmth is most likely caused by heat stress. Crucially, abundant organic benthic foraminiferal linings imply sustained export production, likely driven by prokaryotes. In sharp contrast, the recovery of the CIE yields rapid (<<10 kyr) fluctuations in the abundance of several dinocyst groups, suggesting extreme ecosystem and environmental variability.

  • Open Access English
    Authors: 
    Salabarnada, Ariadna; Escutia, Carlota; Röhl, Ursula; Nelson, C Hans; McKay, Robert M; Jiménez-Espejo, Francisco Jose; Bijl, Peter K; Hartman, Julian D; Ikehara, Minoru; Strother, Stephanie L; +6 more
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: NWO | Reconstructing the the ev... (2300166023), NWO | The Dawn of a Greenhouse ... (2300180216)

    Antarctic ice sheet and Southern Ocean paleoceanographic configurations during the late Oligocene are not well resolved. They are however important to understand the influence of high-latitude Southern Hemisphere feedbacks on global climate under CO2 scenarios (between 400 and 750 ppm) projected by the IPCC for this century, assuming unabated CO2 emissions. Sediments recovered by the Integrated Ocean Drilling Program (IODP) at Site U1356, offshore of the Wilkes Land margin in East Antarctica, provide an opportunity to study ice sheet and paleoceanographic configurations during the late Oligocene (26-25 Ma). Our study, based on a combination of sediment facies analysis, magnetic susceptibility, density, and X-Ray Fluorescence geochemical data, shows that glacial and interglacial sediments are continuously reworked by bottom-currents, with maximum velocities occurring during the interglacial periods. Glacial sediments record poorly ventilated, low-oxygenation bottom water conditions, interpreted to result from a northward shift of westerly winds and surface oceanic fronts. Interglacial sediments record more oxygenated and ventilated bottom water conditions and strong current velocities, which suggests enhanced mixing of the water masses as a result of a southward shift of the Polar Front. Intervals with preserved carbonated nannofossils within some of the interglacial facies are interpreted to form under warmer paleoclimatic conditions when less corrosive warmer northern component water (e.g. North Atlantic sourced deep water) had a greater influence on the Site. Spectral analysis on the late Oligocene sediment interval show that the glacial-interglacial cyclicity and related displacements of the Southern Ocean frontal systems between 26-25 Ma were forced mainly by obliquity. The paucity of iceberg rafted debris (IRD) throughout the studied interval contrasts with earlier Oligocene and post-Miocene Climate Optimum sections from Site U1356 and with late Oligocene strata from the Ross Sea, which contain IRD and evidence for coastal glaciers and sea ice. These observations, supported by elevated sea surface paleotemperatures, the absence of sea-ice, and reconstructions of fossil pollen between 26 and 25 Ma at Site U1356, suggest that open ocean water conditions prevailed. Combined, these evidences suggest that glaciers or ice caps likely occupied the topographic highs and lowlands of the now marine Wilkes Subglacial Basin (WSB). Unlike today, the continental shelf was not over-deepened and thus ice sheets in the WSB were likely land-based and marine-based ice sheet expansion was likely limited to coastal regions.

  • Open Access
    Authors: 
    Agnieszka Płonka;
    Publisher: Zenodo
    Project: NWO | Full waveform inversion f... (2300172344)

    This dataset should provide complete synthetic seismograms and software (python tools for random media generation, signal comparison and histogram stacking) that were used in the publication: Płonka, A., Blom, N., and Fichtner, A.: The imprint of crustal density heterogeneities on regional seismic wave propagation, Solid Earth, 7, 1591-1608, doi:10.5194/se-7-1591-2016, 2016.

  • Authors: 
    Pierik, Harm Jan; Rowin J Van Lanen; Gouw-Bouman, Marjolein TIJ; Groenewoudt, Bert J; Wallinga, Jakob; Hoek, Wim Z;
    Publisher: SAGE Journals
    Project: NWO | The Dark Age of the Lowla... (2300172486)

    Supplemental material, Appendix_A_and_B for Controls on late-Holocene drift-sand dynamics: The dominant role of human pressure in the Netherlands by Harm Jan Pierik, Rowin J van Lanen, Marjolein TIJ Gouw-Bouman, Bert J Groenewoudt, Jakob Wallinga and Wim Z Hoek in The Holocene

  • English
    Authors: 
    Frieling, Joost; Huurdeman, Emiel P; Rem, Charlotte C M; Donders, Timme H; Pross, J��rg; Bohaty, Steven M; Holdgate, Guy R; Gallagher, Stephen John; McGowran, Brian; Bijl, Peter K;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: NWO | The Dawn of a Greenhouse ... (2300180216)

    Detailed, stratigraphically well-constrained environmental reconstructions are available for Paleocene and Eocene strata at a range of sites in the southwest Pacific Ocean (New Zealand and East Tasman Plateau; ETP) and Integrated Ocean Discovery Program (IODP) Site U1356 in the south of the Australo-Antarctic Gulf (AAG). These reconstructions have revealed a large discrepancy between temperature proxy data and climate models in this region, suggesting a crucial error in model, proxy data or both. To resolve the origin of this discrepancy, detailed reconstructions are needed from both sides of the Tasmanian Gateway. Paleocene-Eocene sedimentary archives from the west of the Tasmanian Gateway have unfortunately remained scarce (only IODP Site U1356), and no well-dated successions are available for the northern sector of the AAG. Here we present new stratigraphic data for upper Paleocene and lower Eocene strata from the Otway Basin, southeast Australia, on the (north)west side of the Tasmanian Gateway. We analyzed sediments recovered from exploration drilling (Latrobe-1 drill core) and outcrop sampling (Point Margaret) and performed high-resolution carbon isotope geochemistry of bulk organic matter and dinoflagellate cyst (dinocyst) and pollen biostratigraphy on sediments from the regional lithostratigraphic units, including the Pebble Point Formation, Pember Mudstone and Dilwyn Formation. Pollen and dinocyst assemblages are assigned to previously established Australian pollen and dinocyst zonations and tied to available zonations for the SW Pacific. Based on our dinocyst stratigraphy and previously published planktic foraminifer biostratigraphy, the Pebble Point Formation at Point Margaret is dated to the latest Paleocene. The globally synchronous negative carbon isotope excursion that marks the Paleocene-Eocene boundary is identified within the top part of the Pember Mudstone in the Latrobe-1 borehole and at Point Margaret. However, the high abundances of the dinocyst Apectodinium prior to this negative carbon isotope excursion prohibit a direct correlation of this regional bio-event with the quasi-global Apectodinium acme at the Paleocene-Eocene Thermal Maximum (PETM; 56 Ma). Therefore, the first occurrence of the pollen species Spinizonocolpites prominatus and the dinocyst species Florentinia reichartii are here designated as regional markers for the PETM. In the Latrobe-1 drill core, dinocyst biostratigraphy further indicates that the early Eocene (~56-51 Ma) sediments are truncated by a ~10 Myr long hiatus overlain by middle Eocene (~40 Ma) strata. These sedimentary archives from southeast Australia may prove key in resolving the model-data discrepancy in this region, and the new stratigraphic data presented here allow for detailed comparisons between paleoclimate records on both sides of the Tasmanian Gateway.

  • Open Access
    Authors: 
    Vlietstra, Wytze; Vos, Rein; Sijbers, Anneke; Mulligen, Erik Van; Kors, Jan;
    Publisher: figshare
    Project: NWO | ODEX4all Open Discovery a... (2300182466), NWO | XCiDE: Crossing the Combu... (2300153186)

    Performance for different ratios between the positive and the negative cases in the training set. This file shows the performance on a balanced test set as a function of the ratio of positive and negative cases in the training set. (XLSX 14 kb)

  • Open Access English
    Authors: 
    Lauretano, Vittoria; Littler, Kate; Polling, M; Zachos, James C; Lourens, Lucas Joost;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: NWO | Evolution of astronomical... (2300157723)

    Recent studies have shown that the Early Eocene Climatic Optimum (EECO) was preceded by a series of short-lived global warming events, known as hyperthermals. Here we present high-resolution benthic stable carbon and oxygen isotope records from ODP Sites 1262 and 1263 (Walvis Ridge, SE Atlantic) between ~54 and ~52 million years ago, tightly constraining the character, timing, and magnitude of six prominent hyperthermal events. These events, which include Eocene Thermal Maximum (ETM) 2 and 3, are studied in relation to orbital forcing and long-term trends. Our findings reveal an almost linear relationship between d13C and d18O for all these hyperthermals, indicating that the eccentricity-paced co-variance between deep-sea temperature changes and extreme perturbations in the exogenic carbon pool persisted during these events towards the onset of the EECO, in accord with previous observations for the Paleocene Eocene Thermal Maximum (PETM) and ETM2. The covariance of d13C and d18O during H2 and I2, which are the second pulses of the "paired" hyperthermal events ETM2-H2 and I1-I2, deviates with respect to the other events. We hypothesize that this could relate to a relatively higher contribution of an isotopically heavier source of carbon, such as peat or permafrost, and/or to climate feedbacks/local changes in circulation. Finally, the d18O records of the two sites show a systematic offset with on average 0.2 per mil heavier values for the shallower Site 1263, which we link to a slightly heavier isotopic composition of the intermediate water mass reaching the northeastern flank of the Walvis Ridge compared to that of the deeper northwestern water mass at Site 1262.

  • Open Access English
    Authors: 
    Gürer, Derya; van Hinsbergen, Douwe J J; Özkaptan, Murat; Creton, Iverna; Koymans, Mathijs R; Cascella, Antonio; Langereis, Cornelis G;
    Publisher: PANGAEA - Data Publisher for Earth & Environmental Science
    Project: NWO | Subduction Initiation rec... (2300172509), EC | SINK (306810)

    To quantitatively reconstruct the kinematic evolution of Central and Eastern Anatolia within the framework of Neotethyan subduction accommodating Africa-Eurasia convergence, we paleomagnetically assess timing and amount of vertical axis rotations across the Ulukisla and Sivas regions. We show paleomagnetic results from ~30 localities identifying a coherent rotation of a block - comprising the southern Kirsehir Block, the Ulukisla basin, the Central and Eastern Taurides, and the southern part of the Sivas basin. This block experienced a ~30° counter-clockwise vertical axis rotation since Oligocene time. Sediments in the northern Sivas region show clockwise rotations. We use the rotation patterns together with known fault zones to argue that the counter-clockwise rotating domain of south-central Turkey was bounded by the Savcili Thrust Zone and Deliler-Tecer Fault Zone in the north and by the African-Arabian trench in the south, the western boundary of which is poorly constrained and requires future study. Our new paleomagnetic constraints provide a key ingredient for future kinematic restorations of the Anatolian tectonic collage. We combine our extensive new dataset with existing data (Guerer et al., 2018, and references therein) to identify the dimension of rotating domains in Central and Eastern Anatolia, and identify structures that may have accommodated these rotations. Paleomagnetic interpretations and statistical analyses were carried out using the platform independent portal Paleomagnetism.org (Koymans et al., 2016).

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