--> Abstract: The Upper Devonian Trough from Saoura to Fegaguira, Northwest Sahara, Algeria: Geodynamic and Environmental Aspects, by Fatima Zohra Malti, Ben-Youcef Madani, Abdelkader Abbache, and Mekahli Larbi; #90077 (2008)

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The Upper Devonian Trough from Saoura to Fegaguira, Northwest Sahara, Algeria: Geodynamic and Environmental Aspects

Fatima Zohra Malti1*, Ben-Youcef Madani2, Abdelkader Abbache3, and Mekahli Larbi2
1Bechar University, Algeria
2Oran University, Algeria
3Mascara University, Algeria
*[email protected]

The northern part of the Saoura Valley, in the northwestern Saharan Platform, is located to the 250km northwest of the Fegaguira area, situated around Djebel Hech in Algeria. Palaeozoic deposits, mostly hidden by the “Grand Erg Occidental”, were deposited between Saoura to Fegaguira. This study constructed a paleodynamic Saoura–Fegaguira transect, which documented as Gondwanan trough. The Saoura–Fegaguira Trough is probably the result of the rejuvenation of the Pan-African paleosutures during Caledonian and Hercynian orogenic phases. In the trough the Upper Devonian successions is mainly composed of terrigenous rocks intercalated by minor limestones. The limestones at the base of the Upper Devonian are called “griottes” after their nodulour aspect. The southern Fegaguira part of the trough is filled by argillaceous deposits intercalated with some limestones layers. These thick slumped argillaceous deposits prograded into the deeper part of the trough. The uppermost Devonian layers onlap the edge of the trough and tend to disappear towards the north. The Late Devonian (Frasnian and Lower Famennian) epeirogenesis and sea-level changes are recorded as retrograding systems tracts by the “griottes” limestones. The prograding systems tracts are evident from the slumped Upper Famennian turbidites. The stacked systems tracts form genetic sequences of the second type in the third-order framework of Vail and al. (1987). Sequences of the first type and same order are recorded in the deeper part of the trough. The Saoura-Fegaguira Trough rests on the “Ougartiennes” NW-trending fault network, and forms an unstable tectonic junction zone between the Pan-African and Western African Craton. The trough probably extends several kilometers towards the southeast.

 

AAPG Search and Discovery Article #90077©2008 GEO 2008 Middle East Conference and Exhibition, Manama, Bahrain