Middle and Late Devonian paleogeography of the eastern Anti-Atlas (Morocco)

The eastern Anti-Atlas of Morocco represents one of the most completely exposed and perfectly documented biostratigraphic records of the entire Devonian worldwide. Paleogeographically it is clearly differentiated into shallow basins, pelagic platforms, and land areas which are newly defined and illustrated, one from the top of the Middle Devonian, the other from the middle Famennian as two of the most characteristic intervals. The dominant paleogeographic feature is the T-shaped Tafilalt Platform which, in spite of common unconformities and hiatuses, provides the best-documented biostratigraphic record through the entire Devonian. The westernmost termination of this platform was emerged during most of the Devonian (and locally even earlier) and became only flooded again by the Tournaisian transgression. In contrast to previous interpretations, this area is considered as autochthonous. In the Mader Basin subsidence was up to one hundred times higher with respect to the adjacent platforms, but water depth during the Middle Devonian to middle Famennian interval generally remained above storm-wave base. Devonian rocks are only patchily and incompletely preserved on the Mader Platform, which can be considered as an intermittently flooded peninsula connected to the Lower Paleozoic farther west. The major paleotectonic element of the entire area is the Great Anti-Atlas Fault, a sinistral strike-slip fault, which sharply confines the above-mentioned realms in the south.