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Lithospheric cooling and thickening as a basin forming mechanism

Holt, P.J.; Allen, M.B.; van Hunen, J.; Bjørnseth, H.M.

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Authors

P.J. Holt

H.M. Bjørnseth



Abstract

Widely accepted basin forming mechanisms are limited to flexure of the lithosphere, and lithospheric stretching followed by cooling and thermal subsidence. Neither of these mechanisms works for a group of large basins, sometimes known as “intracontinental sags”. In this paper we investigate cooling and thickening of initially thin lithosphere as a basin forming mechanism, by a combination of forward modelling and a backstripping study of two Palaeozoic North African basins: Ghadames and Al Kufrah. These are two of a family of basins, once unified, which lie over the largely accretionary crust of North Africa and Arabia. Such accretionary crust tends to be juvenile, consisting of amalgamated island arcs, accretionary prisms and melanges, and typically has near-normal crustal thicknesses but initially thin mantle lithosphere. Post-accretion subsidence is modelled using a plate cooling model similar to cooling models for oceanic lithosphere. The crustal composition and thickness used in the models are varied around average values of accretionary crust to represent likely heterogeneity. The model allows the lithosphere to thicken as it cools and calculates the resulting isostatic subsidence. Water-loaded tectonic subsidence curves from these forward models are compared to tectonic subsidence curves produced from backstripped wells from Al Kufrah and Ghadames Basins. A good match between the subsidence curves for the forward model and backstripping is produced when the best estimates for the crustal structure, composition and the present day thickness of the lithosphere for North Africa are used as inputs for the forward model. The model produces sediment loaded basins of 2–7 km thickness for the various crustal assemblies over ~ 250 Myr. This shows that lithospheric cooling provides a viable method for producing large basins with prolonged subsidence, without the need for initial extension, provided the condition of initially thin mantle lithosphere is met.

Citation

Holt, P., Allen, M., van Hunen, J., & Bjørnseth, H. (2010). Lithospheric cooling and thickening as a basin forming mechanism. Tectonophysics, 495(3-4), 184-194. https://doi.org/10.1016/j.tecto.2010.09.014

Journal Article Type Article
Publication Date Dec 3, 2010
Deposit Date Jul 22, 2011
Publicly Available Date Mar 13, 2015
Journal Tectonophysics
Print ISSN 0040-1951
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 495
Issue 3-4
Pages 184-194
DOI https://doi.org/10.1016/j.tecto.2010.09.014
Keywords Basin, Lithosphere, Subsidence, North Africa.

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Copyright Statement
NOTICE: this is the author’s version of a work that was accepted for publication in Tectonophysics. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Tectonophysics, 495, 3-4, 3 December 2010, 10.1016/j.tecto.2010.09.014.







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