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Depositional Previous HitSequenceNext Hit Evolution, Paleozoic and Early Mesozoic of the Central Saharan Platform, North Africa

SPRAGUE, ANTHONY R. G., Exxon Production Research Company, Houston, TX

Over 30 depositional Previous HitsequencesNext Hit have been identified in the Paleozoic and lower Mesozoic of the Ghadames basin of eastern Algeria, southern Tunisia, and western Libya. Well logs and lithologic information from more than 500 wells were used to correlate the 30 Previous HitsequencesNext Hit throughout the basin (total area more than 1 million km2). Based on systematic changes in the log response of strata in successively younger Previous HitsequencesNext Hit, five groups of Previous HitsequencesNext Hit with distinctive characteristics have been identified: Cambro-Ordivician, Upper Silurian-Middle Devonian, Upper Devonian, Carboniferous, and Middle Triassic-Middle Jurassic. Each Previous HitsequenceNext Hit group is terminated by a major, tectonically enhanced Previous HitsequenceNext Hit boundary that is immediately overlain (except for the Carboniferous) by a shale-prone interval dep sited in response to basin-wide flooding. The four Paleozoic Previous HitsequenceNext Hit groups were deposited on the Saharan platform, a north-facing, clastic-dominated shelf that covered most of North Africa during the Paleozoic. The Previous HitsequenceNext Hit boundary at the top of the Carboniferous Previous HitsequenceNext Hit group is one of several Permian-Carboniferous angular unconformities in North Africa related to the Hercynian orogeny. The youngest Previous HitsequenceNext Hit group (Middle Triassic to Middle Jurassic) is a clastic-evaporite package that onlaps southward onto the top Paleozoic Previous HitsequenceNext Hit boundary. In this group, the lowstand systems tract in each Previous HitsequenceNext Hit is characterized by a well-developed basinward facies change from sandprone, nonmarine (brain-plain) deposits to an anhydrite-halite succession deposited in a restricted shallow shelf nvironment. The progressive changes, from the Cambrian to the Jurassic, in the nature of the Ghadames basin Previous HitsequencesTop is a reflection of the interplay between basin morphology and tectonics, vegetation, eustasy, climate, and sediment supply.

 

AAPG Search and Discovery Article #91007© 1991 AAPG International Conference, London, England, September 29-October 2, 1991 (2009)