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An attempt to constrain the age, duration, and eruptive history of the Karoo flood basalt: Naude's Nek section (South Africa)

Moulin, Maud; Fluteau, Frédéric; Courtillot, Vincent; Marsh, Julian; Delpech, Guillaume; Quidelleur, Xavier; Gérard, Martine and Jay, Anne E. (2011). An attempt to constrain the age, duration, and eruptive history of the Karoo flood basalt: Naude's Nek section (South Africa). Journal of Geophysical Research: Planets, 116(B7), article no. B07403.

DOI (Digital Object Identifier) Link: https://doi.org/10.1029/2011JB008210
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Abstract

We have carried out paleomagnetic sampling of a ∼750 m sequence of the Karoo large igneous province (Naude's Nek Pass, South Africa). K-Ar dating (Cassignol-Gillot) has been performed on four samples from the 650 m upper unit (mean age 179.2 ± 1.8 Ma) and a sample from the lower unit (184.8 ± 2.6 Ma). A succession of two phases of volcanism is suggested. The lower 25 flows (115 m thick) have recorded a reversed polarity; the next 23 flows (135 m thick) are transitional and contribute a detailed record of the “Van Zijl” (1962) Jurassic reversal. The upper 38 flows (500 m thick) have normal polarity. Directional groups (DGs) of lava flows with quasi-identical remanence directions indicate eruption durations too short to have recorded geomagnetic secular variation and hence are interpreted as single eruptive events. Altogether, 19 DGs and 10 sheet lobes yield a sequence of 29 distinct directions. This could correspond to a total eruptive activity shorter than 3000 years, less than one per mil of the total duration over which the section was emplaced. We obtain a new paleomagnetic pole for South Africa at ∼180 Ma (λ = 75.2°N, ϕ = 276.4°E, A95 = 5.8°, N = 19), which is consistent with earlier reports.

Item Type: Journal Item
Copyright Holders: 2011 by the American Geophysical Union
ISSN: 2156-2202
Extra Information: 27 pp.
Keywords: Karoo; eruptive sequence; geochronology (K-Ar); large igneous province; magnetostratigraphy
Academic Unit/School: Faculty of Science, Technology, Engineering and Mathematics (STEM) > Environment, Earth and Ecosystem Sciences
Faculty of Science, Technology, Engineering and Mathematics (STEM)
Item ID: 41265
Depositing User: Anne Jay
Date Deposited: 10 Nov 2014 15:50
Last Modified: 07 Dec 2018 10:26
URI: http://oro.open.ac.uk/id/eprint/41265
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