Field-based investigations of an 'Infracambrian' clastic succession in SE Libya and its bearing on the evolution of the Al Kufrah Basin

Le Heron, Daniel Paul and Howard, James P. and Alhassi, Aiyad Mohamed and Anderson, Lester and Morton, Andrew and Fanning, C. Mark (2009) Field-based investigations of an 'Infracambrian' clastic succession in SE Libya and its bearing on the evolution of the Al Kufrah Basin. Geological Society, London, Special Publications, 326 (1). pp. 193-210. DOI 10.1144/SP326.10

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Abstract

Field-based investigation of Infracambrian' rocks cropping out on the eastern flank of Al Kufrah Basin (area 500 000 km2) reveals a an approximately 500 m-thick clastic succession of massive and cross-bedded sandstones, separated by 60 m-thick mudrock intervals. New zircon age data indicate a maximum age of deposition of approximately 950 Ma; furthermore, the absence of zircons of Pan-African age suggests a minimum depositional age older than the Pan-African Orogeny. Previously unreported folding and spaced cleavage affects these deposits to produce a pronounced NE-SW-striking tectonic grain that is interpreted to result from NW-SE-directed orthogonal compression during the Pan-African Orogeny. These Infracambrian rocks are therefore unlikely to be suitable analogues for weakly deformed strata shown to exist beneath the Cambro-Ordovician strata of the Al Kufrah Basin. Earlier work mapped a series of Infracambrian marble outcrops along strike of the clastic deposits; thin section petrography reveals that some of these are basic igneous rocks metamorphosed to greenschist facies. Interpretation of gravity data over the Al Kufrah Basin shows NE-SW-striking faults, parallel to outcrop structures, and secondary NW-SE faults. The data do not support earlier interpretations of a rhomboidal geometry in the deep subsurface of the basin, which has previously been attributed to strike-slip (pull-apart) processes. This research impacts on earlier suggestions that the Al Kufrah Basin opened as one of a series of en echelon pull-apart basins situated along a 6000 km-long shear zone known as the Transafrican Lineament, stretching from the Nile to the Niger Delta.

Item Type: Article
Uncontrolled Keywords: 09AREP;
Subjects: 02 - Geodynamics, Geophysics and Tectonics
Divisions: 02 - Geodynamics, Geophysics and Tectonics
Journal or Publication Title: Geological Society, London, Special Publications
Volume: 326
Page Range: pp. 193-210
Identification Number: 10.1144/SP326.10
Depositing User: Sarah Humbert
Date Deposited: 08 Mar 2010 22:44
Last Modified: 23 Jul 2013 09:56
URI: http://eprints.esc.cam.ac.uk/id/eprint/1337

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