HR: 0800h
AN: T31B-0478    [Abstracts]
TI: Recent faulting and active shortening of the Middle Atlas Mountains, Morocco, within the diffuse African-Eurasian plate boundary
AU: * Rigby, M
EM: rigby.mike@gmail.com
AF: Department of Geological Sciences, 101 Geology Building University of Missouri, Columbia, MO 65211, United States
AU: Gomez, F
EM: fgomez@missouri.edu
AF: Department of Geological Sciences, 101 Geology Building University of Missouri, Columbia, MO 65211, United States
AU: Zakir, A
EM: zakirabdou@yahoo.fr
AF: AlphaGeo Petroleum Exploration, B.P. 8136, Rabat, 00000, Morocco
AU: Hahou, Y
EM: hahou@cnrst.ma
AF: Institut National de Geophysique, Centre National Pour la Recherche Scientifique et Technique, Rabat, 00000, Morocco
AU: Jabour, N
EM: jabour@cnrst.ma
AF: Institut National de Geophysique, Centre National Pour la Recherche Scientifique et Technique, Rabat, 00000, Morocco
AB: The NE-SW trending Middle Atlas Mountains are an active intracontinental mountain belt within the diffuse African – Eurasian plate boundary. The mountain belt is obliquely oriented to the NNW-SSE direction of Late Cenozoic plate convergence. Both shear and compressional features are exhibited with apparent slip partitioning: Folding and thrusting is concentrated in the Folded Middle Atlas, whereas strike-slip dominates in the Tabular Middle Atlas. In the central part of the Folded Middle Atlas, fault scarps of Quaternary alluvium, including a 4.5 meter (probably composite) scarp and a 1 meter (possibly single event) scarp, attest to recent faulting along the mountain front. Detailed topographic mapping of the scarps provides a basis for geomorphic analysis and degradation modeling. Furthermore, the reconstruction of longitudinal stream terrace profiles helps constrain a long term deformation history. Radiocarbon and pending cosmogenic dates provide age constraints on the faulted surfaces and the multiple stream terraces in the area. To place these active tectonic observations in a larger context, the fault and fold geometry has been assessed by completing a 10 km structural transect across the frontal thrust, providing basis for the construction of a balanced cross-section. By combining the structural geometry with the uplift rate, a minimum estimate of the rate of horizontal shortening in the Middle Atlas can be evaluated. Preliminary results suggest the Middle Atlas may accommodate 5 – 10 percent of the total 4.5 mm/yr convergence between the African and Eurasian plates. These results demonstrate that the Middle Atlas Mountains are a integral part of the diffuse plate boundary, as well as suggesting a modest level of earthquake hazard in the region.
DE: 8002 Continental neotectonics (8107)
DE: 8005 Folds and folding
DE: 8102 Continental contractional orogenic belts and inversion tectonics
DE: 8108 Continental tectonics: compressional
SC: Tectonophysics [T]
MN: 2007 Fall Meeting