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    Continental crust beneath the Agulhas Plateau, southwest Indian Ocean

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    TucholkeEtAl1981.pdf (1.294Mb)
    Date
    1981-05-10
    Author
    Tucholke, Brian E.  Concept link
    Houtz, Robert E.  Concept link
    Barrett, Douglas M.  Concept link
    Metadata
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    Citable URI
    https://hdl.handle.net/1912/5787
    As published
    https://doi.org/10.1029/JB086iB05p03791
    DOI
    10.1029/JB086iB05p03791
    Abstract
    The Agulhas Plateau lies 500 km off the Cape of Good Hope in the southwestern Indian Ocean. Acoustic basement beneath the northern one third of this large, aseismic structural high has rugged morphology, but basement in the south is anomalously smooth, excepting a 30- to 90-km-wide zone with irregular relief that trends south-southwest through the center of the plateau. Seismic refraction profiles across the southern plateau indicate that the zone of irregular acoustic basement overlies thickened oceanic crust and that continental crust, locally thinned and intruded by basalts, underlies several regions of smooth acoustic basement. Recovery of quartzo-feldspathic gneisses in dredge hauls confirms the presence of continental crust. The smoothness of acoustic basement probably results from erosion (perhaps initially subaerial) of topographic highs with redeposition and cementation of debris in ponds to form high-velocity beds. Basalt flows and sills also may contribute locally to form smooth basement. The rugged basement of the northern plateau appears to be of oceanic origin. A plate reconstruction to the time of initial opening of the South Atlantic places the continental part of the southern plateau adjacent to the southern edge of the Falkland Plateau, and both abut the western Mozambique Ridge. Both the Agulhas and Falkland plateaus were displaced westward during initial rifting in the Early Cretaceous. Formation of an RRR triple junction at the northern edge of the Agulhas continental fragment during middle Cretaceous time may explain the origin of the rugged, thickened oceanic crust beneath the northern plateau as well as the apparent extension of the continental crust and intrusion of basaltic magmas beneath the southern plateau.
    Description
    Author Posting. © American Geophysical Union, 1981. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 86, no. B5 (1981): 3791–3806, doi:10.1029/JB086iB05p03791.
    Collections
    • Geology and Geophysics (G&G)
    Suggested Citation
    Journal of Geophysical Research 86, no. B5 (1981): 3791–3806
     
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