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4 Research products, page 1 of 1

  • Digital Humanities and Cultural Heritage
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  • Netherlands Organisation for Scientific Research (NWO)
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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: NWO | Evolution of astronomical... (2300157723), EC | ERAS (293741), EC | EARTHSEQUENCING (617462)

    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.

  • Open Access English
    Authors: 
    Frieling, Joost; Reichart, Gert-Jan; Middelburg, Jack J; Röhl, 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 ºC surface ocean warming from the uppermost Paleocene to peak PETM, of which ~1 ºC 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: 
    Sluijs, Appy; Bijl, Peter K; Schouten, Stefan; Röhl, 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.

  • Open Access English
    Authors: 
    de Rijke, Maarten; Jijkoun, Valentin; Laan, Fons; Weerkamp, Wouter; Ackermans, Paul; Geleijnse, Gijs;
    Publisher: Springer Berlin Heidelberg
    Project: NWO | DutchSemCor: 1 million te... (2300154091), EC | PROMISE (258191), NWO | Semantic Search in E-Disc... (2300168486), NWO | Content-based Literature ... (2300152116), NWO | Building Rich Links to En... (2300153702), EC | LIMOSINE (288024)