Middle Devonian Reefs in Spanish Sahara

Abstract

Abstract An interesting comparison can be drawn between the Spanish Saharan reefs and those of equivalent age in the Rainbow area of northwestern Alberta. They are of similar shape, size and distribution, and of comparable lithologic and ecologic constitution, suggesting similar environments of deposition in these two widely separated areas. Middle Devonian rocks are exposed almost continuously in eastern Spanish Sahara along the southeast flank of the Tindouf basin. Fine elastics predominate with several thin carbonate horizons, three of which develop locally into biohermal limestone reefs. These played an important part in controlling the pattern of sedimentation around them, and there is evidence of differential loading and compaction of the underlying and overlying strata. The study of these bioherms and their back-reef and off-reef facies is aided by the very gentle homoclinal structure of the area, the lack of vegetation, and by their being exhumed by the removal of the surrounding shale. The reefs exposed in spectacular fashion near Gor Loutad and Uein Terguet are briefly described and related to their paleo-environment.