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  • 1
    Publication Date: 2019-02-01
    Description: During the Late Cretaceous and early Cenozoic the Earth experienced prolonged climatic cooling most likely caused by decreasing volcanic activity and atmospheric CO2 levels. However, the causes and mechanisms of subsequent major global warming culminating in the late Paleocene to Eocene greenhouse climate remain enigmatic. We present deep and intermediate water Nd-isotope records from the North and South Atlantic to decipher the control of the opening Atlantic Ocean on ocean circulation and its linkages to the evolution of global climate. The marked convergence of Nd-isotope signatures 59 million years ago indicates a major intensification of deep-water exchange between the North and South Atlantic, which coincided with the turning point of deep-water temperatures towards early Paleogene warming. We propose that this intensification of Atlantic overturning circulation in concert with increased atmospheric CO2 from continental rifting marked a climatic tipping point contributing to a more efficient distribution of heat over the planet.
    Type: Article , PeerReviewed
    Format: text
    Format: text
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  • 2
    Publication Date: 2018-03-06
    Description: We present and illustrate a workflow to produce palaeobathymetric reconstructions, using examples from the South Atlantic Ocean. With a recent high-resolution plate kinematic model as the starting point, we calculate an idealized basement surface by applying plate-cooling theory to seafloor ages and integrating the results with depths along the extended continental margins. Then, we refine the depths of this basement surface to account for the effects of sedimentation, variations in crustal thickness and dynamic topography. Finally, the corrected idealized surface is cut along appropriate plate outlines for the desired time slice and reconstructed using appropriate Euler parameters. In order to assess the applicability of modelled results, we critically examine the limitations and uncertainties resulting from the datasets used and assumptions made. Palaeobathymetry modelled with our approach is likely to be least reliable over parts of large igneous provinces close to the times of their eruption, and most reliable within the oceanic interiors for Neogene time slices. The uncertainty range is not smaller than 500 m for any significant region at any time, and its mean over 95% of locations in all time slices is close to 1800 m.
    Print ISSN: 0305-8719
    Electronic ISSN: 2041-4927
    Topics: Geosciences
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  • 3
    Publication Date: 2017-01-01
    Description: Digital grids of basement age of the world's oceans are essential for modern geodynamic and paleoceanographic studies. Any such grid is built using a plate kinematic model, whose accuracy and reliability directly influence the accuracy and reliability of the grid. We present a seafloor age grid for the South Atlantic based on a recent high-resolution plate kinematic model. The grid is built from a data set of points whose ages are defined in or for the plate kinematic model, incorporating breaks at tectonic boundaries like fracture zones where the age function is discontinuous. We compare predictions of the new grid and of a previously published one, which is based on an older plate kinematic model, to magnetic isochron pick data sets. The comparison shows the new grid to provide a more reliable depiction of seafloor age in the South Atlantic. Numerical estimates of the new grid's uncertainty are determined by interpolation between (1) misfits at grid cells coinciding with magnetic isochron ages, (2) misfits implied by locational uncertainties in predicted isochrons propagated from uncertainties in the plate kinematic model, and (3) by the proximities of cells to fracture zone traces or ridge-jump scars. Estimated total uncertainty is 〈10 My for 94% of the grid and 〈5 My for 72%, but much larger in areas where magnetic anomaly data are scarce (such as the Cretaceous Normal Superchron) and in the vicinity of long-offset fracture zones. © 2017. American Geophysical Union. All Rights Reserved.
    Electronic ISSN: 1525-2027
    Topics: Chemistry and Pharmacology , Geosciences , Physics
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  • 4
    Publication Date: 2018
    Description: 〈p〉We present and illustrate a workflow to produce palaeobathymetric reconstructions, using examples from the South Atlantic Ocean. With a recent high-resolution plate kinematic model as the starting point, we calculate an idealized basement surface by applying plate-cooling theory to seafloor ages and integrating the results with depths along the extended continental margins. Then, we refine the depths of this basement surface to account for the effects of sedimentation, variations in crustal thickness and dynamic topography. Finally, the corrected idealized surface is cut along appropriate plate outlines for the desired time slice and reconstructed using appropriate Euler parameters.〈/p〉 〈p〉In order to assess the applicability of modelled results, we critically examine the limitations and uncertainties resulting from the datasets used and assumptions made. Palaeobathymetry modelled with our approach is likely to be least reliable over parts of large igneous provinces close to the times of their eruption, and most reliable within the oceanic interiors for Neogene time slices. The uncertainty range is not smaller than 500 m for any significant region at any time, and its mean over 95% of locations in all time slices is close to 1800 m.〈/p〉
    Print ISSN: 0375-6440
    Electronic ISSN: 2041-4927
    Topics: Geosciences
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