--> --> Abstract: Structural and Climatic Control from the Deposition of the Oukaimeden Sandstone, High Atlas, Morocco, by Ivan Fabuel-Perez, Catherine Baudon, and Jonathan Redfern; #90082 (2008)

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Structural and Climatic Control from the Deposition of the Oukaimeden Sandstone, High Atlas, Morocco

Ivan Fabuel-Perez, Catherine Baudon, and Jonathan Redfern
SEAES, NARG - Manchester University, Manchester, United Kingdom

The Upper Triassic Oukaimeden Formation, located in the High Atlas of Morocco, comprises a thick fluvio-aeolian succession. These outcrops are an important analogue for the TAGI Formation (Triassic Argilo-Gréseux Inférieur), representing one of the most productive siliciclastic reservoirs in central Algeria. The Oukaimeden Basin formed as a rift basin bounded by normal faults and influenced by the reactivation of Hercynian structures. Its geodynamic evolution was linked to the Altantic rifting to the West and the formation of the Tethys to the North, which led to the development of ENE and NNE striking normal faults. The present day geometry reflects the inversion of the rift-grabens due to the Alpine compression that led to major uplifts in the High Atlas and subsequent erosion. The Oukaimeden Formation is interpreted to have been deposited in an active rift setting dominated by ephemeral/perennial braided fluvial conditions with possible marine influence towards the top of the formation and an overall vertical evolution towards more arid conditions. This study shows that the facies distribution is controlled by an interaction of tectonic and climatic controls. The ENE striking faults control the basin dimensions and geometry in half-graben as well as the accommodation space for sediments deposition. NNE oriented faults are interpreted to be contemporaneous to the main set.
Evidence of syn-sedimentary movements of both sets are observed as stratigraphic thickening associated to progressive change in dip of the bedding and the presence of breccia deposits towards the fault planes. An integrated study comparing this formation to the one deposited under similar climatic conditions in the Argana Basin allows the relative influence of tectonic versus climate on the sedimentation to be investigated.

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