BIROn - Birkbeck Institutional Research Online

    Post break-up tectonic inversion across the southwestern cape of South Africa: new insights from apatite and zircon fission track thermochronometry

    Wildman, M. and Brown, R. and Watkins, R. and Carter, Andrew and Gleadow, A. and Summerfield, M. (2015) Post break-up tectonic inversion across the southwestern cape of South Africa: new insights from apatite and zircon fission track thermochronometry. Tectonophysics 654 , pp. 30-55. ISSN 0040-1951.

    [img] Text
    12091.pdf - Author's Accepted Manuscript
    Restricted to Repository staff only
    Available under License Creative Commons Attribution.

    Download (2MB)
    [img]
    Preview
    Text
    12091a.pdf - Published Version of Record
    Available under License Creative Commons Attribution.

    Download (5MB) | Preview

    Abstract

    The south-west African margin is regarded as an example of a passive continental margin formed by continental rifting following a phase of lithospheric extension and thinning. Recent attention focused on this margin has included theoretical modelling studies of rift processes, plate kinematic studies of the opening geometry and timing, and empirical studies focused on documenting the crustal structure and offshore sedimentary record. Here, we examine the onshore geomorphic and tectonic response to rifting and breakup, with a specific focus on the SW Cape of South Africa. We present 75 new apatite and 8 new zircon fission track analyses from outcrop samples and onshore borehole profiles along the western margin of South Africa. The data are used to derive robust thermal histories that record two discrete phases of accelerated erosional cooling during the Early Cretaceous (150-130 Ma) and Late Cretaceous (100-80 Ma), respectively. Both periods of enhanced erosion are regional in extent, involved km-scale erosion, and extend well inland of the current escarpment zone, albeit with spatially variable intensity and style. The Late Cretaceous episode is also expressed more locally by tectonic reactivation and inversion of major faults causing km-scale differential displacement and erosion. The new AFT data do not exclude the possibility of modest surface uplift occurring during the Cenozoic, but they restrict the depth of regional Cenozoic erosion on the western margin to less than c. 1 km. The inferred pattern and chronology of erosion onshore is consistent with the key features and sediment accumulation patterns within the offshore Orange and Bredasdorp basins. It is suggested that the Late Cretaceous event was triggered by a combination of regional dynamic uplift augmented along the western margin and in the SW Cape by local tectonic forces arising from dextral displacement of the Falkland Plateau along the Falkland-Agulhas Fracture Zone.

    Metadata

    Item Type: Article
    Keyword(s) / Subject(s): Fission track, Continental margin, Thermal history modelling, southwestern Africa, thermochronology
    School: Birkbeck Schools and Departments > School of Science > Earth and Planetary Sciences
    Depositing User: Administrator
    Date Deposited: 12 May 2015 07:26
    Last Modified: 11 Oct 2016 11:55
    URI: http://eprints.bbk.ac.uk/id/eprint/12091

    Statistics

    Downloads
    Activity Overview
    128Downloads
    134Hits

    Additional statistics are available via IRStats2.

    Archive Staff Only (login required)

    Edit/View Item Edit/View Item