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Stratigraphic architecture of the Devonian succession in the Ghadamis basin of western Libya – correlation with the Illizi basin in Algeria

Abstract : During Palaeozoic times, the structuring of North Gondwana induced the formation large epicratonic platforms in North Africa. These platforms are comprised of extensive, shallow sub-basins or swales separated by smooth tectonic arches. The sub-basins were slowly subsiding whereas the arches were periodically eroded by tectonic uplift or eustatic sea-level drops. The resulting architecture of sedimentary rocks into these basins is characterized by thin, laterally extensive, mixed marine and non marine sediment wedges truncated by large unconformities representing long time gaps. The aims are here (1) to illustrate this typical architecture from the example of the Devonian rocks preserved in the Ghadamis basin and the Illizi basins (2) to discuss the observed geometries of the sediment bodies wedging out along the local tectonic arches of Gargaf and Tihemboka, and (3) to examine the origin and the influence of the parameters that control both the sequence architecture and the reservoir distribution on such large cratonic areas. The Devonian formations are among the largest oil reservoirs in Northern Africa. The Devonian rocks are characterized by the intercalation of sandstones, claystones and shales interbedded with few carbonate beds. They represent a broad range of depositional environments from fluvial to offshore marine shelf organized into a complex stack of tens of m-thick, unconformity-bounded, transgressive-regressive sequences. The architecture of the sedimentary units, reconstructed from the correlation of field observations and subsurface data (wells and seismic data), shows that fluvial and shoreface sandstones units are well-developed close to the arches and thin out laterally in the shale unit that thicken and deepen towards basins depocenters. Offshore marine, organic-rich shale units (secondary source rocks and seals) are prominent marker beds followed along hundreds of km from Libya to Algeria, and possibly further, when they correlate to the Kaçak and Kellwasser events.
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Conference papers
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Submitted on : Thursday, April 16, 2009 - 1:56:08 PM
Last modification on : Tuesday, December 3, 2019 - 5:24:10 PM

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Jean-Noël Proust, M. Ben Rahuma, R. Eschard. Stratigraphic architecture of the Devonian succession in the Ghadamis basin of western Libya – correlation with the Illizi basin in Algeria. Sedimentary Basin of Libya, 4th Symposium, The Geology of southern Libya, Nov 2008, Tripoli, Libya. ⟨insu-00375944⟩

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