The lithostratigraphic subdivision of the Proterozoic basement rocks of the Mudiyah–Mukalla area, Yemen

Abstract

The Precambrian basement rocks between Mudiyah and Mukalla, Yemen are lithostratigraphically divided into the Ahwar and Gharish supergroups and the Tha’lab and Ghabar groups. The age of the basement rocks range from Paleoproterozoic to Neoproterozoic. The late Archean–Paleoproterozoic Ahwar supergroup comprises the Khashab and Barak groups, which were metamorphosed to the upper amphibolite facies and folded within the ‘Irqah phase. It was representing old crystalline zone, marked by monotonous lithological succession, and shows irregular folding and boudinage. The Gharish supergroup is of Meso- to Neoproterozoic age and displays a broad range of metamorphic assemblages from upper amphibolite to greenschist facies. It comprises the Fahman, the Al-Aswad, and the Hatib groups and was subjected to monoclinal and sigmoidal folding. The lithologic succession of the Gharish supergroup reflects a young crystalline zone, punctuated by episodes of orogenic tectonism among the Mahfid, Ludiyah, and ‘Awarid phases. The Tha’lab and Ghabar groups represent the uppermost lithostratigraphical units of Neoproterozoic to Early Cambrian age and formed by low to non-metamaorphic volcanics of the Tha’lab group and by anchi-metamorphic sediments of the Ghabar group. The Tha’lab group contains the youngest volcanic rocks of the basement complex, which were formed after the ‘Awarid main folding phase. The Ghabar group consists of molasse-like deposits formed within small late orogenic basin. It represents a transitional stage between Proterozoic basement and sedimentary platform development, which faulted, folded and partly cleaved within the Ghabar folding phase. The geological and structural evolution of the intrusive rocks recognized that the granitoids can generally divided into the following stages; the anatectic stage of the Ahwar supergroup, the syntectonic stage of the Gharish supergroup, the posttectonic stage of the Tha’lab group and the late orogenic stage of the Ghabar group.