Late Moscovian phylloid algal-microbial mounds from Wadi Araba, north Eastern Desert, Egypt: a new construction model and paleogeographic distribution

Upper Carboniferous deposits of the Rod El-Hamal Formation are well exposed at Wadi Araba, north Eastern Desert, Egypt. The upper part of the Formation includes late Moscovian (Middle Pennsylvanian) mounds formed by filamentous microbes and phylloid algae. Phylloid algae are loosely accumulated and supported by micritic encrustations that were formed by filamentous microbes. The filamentous microbes growing perpendicularly to the phylloid algal surfaces produced concentrated areas of peloids-A (peloid-A aggregations). The spaces between the phylloid algal-microbial frameworks were filled with concentrated areas of peloids-B (peloid-B aggregations) oriented perpendicular to the phylloid algae surfaces. Microbial communities as well as phylloid algae constitute significant components in the late Moscovian buildups in the study area. Below and above the mound facies, the non-reefs carbonates of Unit (IV) of the Rod El-Hamal Formation are composed of molluscan wackestone, ferruginous-molluscan packstone, and bioclastic rudstone facies, reflecting shallow subtidal depositional environment. Pennsylvanian phylloid algal-bearing buildups were divided into Tethyan and Pangean buildups. The Tethyan buildups are widely distributed in the circum-equatorial tropical paleolatitudes. The Egyptian buildups exhibit similarity in the building organisms to those of the Tethyan, but with a higher proportion of microbialites. Therefore, the subtropical Egyptian buildups are regarded as a sub-type of the tropical Tethyan buildups.