Abstract

Seismic anisotropy from the southern African mantle has been inferred from shear-wave splitting measured at 79 sites of the Southern African Seismic Experiment. These data provide the most dramatic support to date that Archean mantle deformation is preserved as fossil mantle anisotropy. Fast polarization directions systematically follow the trend of Archean structures and splitting delay times exhibit geologic control. The most anisotropic regions are Late-Archean in age (Zimbabwe craton, Limpopo belt, western Kaapvaal craton), with delay times reduced dramatically in off-craton regions to the southwest and Early-Archean regions to the southeast. While thin lithosphere can account for weak off-craton splitting, small or vertically incoherent anisotropy is a more likely explanation for the Early-Archean region. We speculate that this difference in on-craton anisotropic structure is the result of two different continent-forming processes operating.

Department(s)

Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Biological materials preservation; Deformation; Seismology; Shear flow; Shear waves; Structural geology; Anisotropy; Earth atmosphere; Polarization; Shale; Shear waves; Anisotropic structure; Delay Time; Geologic control; Mantle deformation; Polarization direction; Shear wave splitting; Zimbabwe Craton

Geographic Coverage

Southern Africa

International Standard Serial Number (ISSN)

0094-8276

Document Type

Article - Journal

Document Version

Final Version

File Type

text

Language(s)

English

Rights

© 2001 American Geophysical Union (AGU), All rights reserved.

Included in

Geology Commons

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