North African Rift Systems: Comparison of Cenozoic Red Sea and Triassic/Jurrasic High Atlas of Morocco

By

 John E. Warme¹

(1) Colorado School of Mines, Golden, CO

 The Cenozoic Red Sea and Mesozoic Atlas continental rift systems have similar lengths, widths and rift tectonic frameworks. They each contain early rift continental beds and evaporites, were flooded by marine waters, and exhibit a facies mosaic representing marine environments that were controlled by local rift tectonics and global eustatics.

Whereas sediments in the modern Red Sea are still accumulating in the syn-rift stage, those of the Mesozoic rift were inverted to form the continuous mountain belt now represented by the almost east-west ranges of the Moroccan High Atlas, Algerian Saharan Atlas, and Tunesian Atlas.

Post-Mesozoic tectonic inversion in the Central and Eastern High Atlas of Morocco exhibit exposures of the Late Triassic dry-rift continental facies and superb outcrops of the Jurassic wet-rift marine facies. The Jurassic facies are limestones and marls, controlled mainly by fault-block tectonics and Toarcian eustatic sea-level rise, and secondarily by hundreds of cycles of deposition the respond to a hierarchy of higher-frequency sea-level fluctuations. The cycles are exhibited in paleoenvironments that represent sabkha, shallow-platform, platform edge with reefs, platform margin with olistoliths, deep basins with turbidites, and isolated platforms with sponge-algal buildups.

Each of these facies produces hydrocarbons in various rifts and other carbonate habitats worldwide. The High Atlas of Morocco is thus an inverted rift whose exposed formations can be compared to those forming in the modern Red Sea, as well as a model for understanding hydrocarbon accumulations in syntectonic formations preserved in subsurface rifts and other dynamic carbonate environments around the globe.