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Book Chapter

Pleistocene to Recent rejuvenation of the Hebron Fault, SW Namibia

By
Stephen White
Stephen White
Geological Survey of Western Australia, 100 Plain Street, East Perth WA 6004, Australia
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Harald Stollhofen
Harald Stollhofen
GeoZentrum Nordbayern, FG Krustendynamik, Universität Erlangen, Schlossgarten, 5, 91054 Erlangen, Germany
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Ian G. Stanistreet
Ian G. Stanistreet
Department of Earth and Ocean Sciences, University of Liverpool, Brownlow Street, PO Box 147, Liverpool, L69 3BX, UK
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Volker Lorenz
Volker Lorenz
Institut für Geologie, Universität Würzburg, Pleicherwall 1, D-97070 Würzburg, Germany
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Published:
January 01, 2009

Abstract

The Hebron Fault in SW Namibia is associated with a <1 m to 9.6 m high scarp displacing Proterozoic basement and Middle to Late Pliocene crystalline conglomerates. The young age of strata exposed in the fault scarp together with evidence for displacement of aeolian dunes, post-dating the Middle Stone Age, suggests that latest fault displacements occurred during the Late Pleistocene to recent. Recorded historical seismic events show that the fault zone is still active. Latest movements of the fault are recorded by: down-to-the-SW offset of calcrete-cemented conglomerate; fluvially modified, asymmetric hanging wall, graben-like structures; at least two left-stepping jogs in the fault trace and structural data from basement rocks in which late-stage crush zones overprint earlier cataclasite. These features provide consistent evidence that the present scarp formed predominantly by normal dip-slip displacement on a NW-striking, steeply SW-dipping master fault with only a minor dextral strike-slip component. Strongly veined cataclastic fault rocks adjacent to the scarp in basement most probably originated at depths of 4–10 km. The conclusion is therefore that recent fault activity has reactivated a pre-existing, much older fault.

Aerial photographic lineaments and similar fault scarps identified NW and SE of the present study area are interpreted as extensions of the same fault structure. Hence the total length of the Hebron Fault is at least 300 km subparallel to the Atlantic margin of southern Africa. Our observations confirm that the Hebron Fault is a neotectonic feature of regional significance that may relate to late Cenozoic and particularly Quaternary neotectonic activity in NE Namibia and NW Botswana.

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Contents

Geological Society, London, Special Publications

Palaeoseismology: Historical and Prehistorical Records of Earthquake Ground Effects for Seismic Hazard Assessment

K. Reicherter
K. Reicherter
RWTH Aachen University, Germany
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A. M. Michetti
A. M. Michetti
Università dell’Insubria, Italy
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P. G. Silva
P. G. Silva
Universidad de Salamanca, Spain
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Geological Society of London
Volume
316
ISBN electronic:
9781862395640
Publication date:
January 01, 2009

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