PALEOENVIRONMENTAL ANALYSIS AND CYCLICITY OF THE MUSTAHIL FORMATION (CRETACEOUS OF CENTRAL SOMALIA)

Abstract

The Cretaceous Mustahil Formation is a marlstone-limestone unit, outcropping typically in the Fafan Valley of Ogaden (eastern Africa). A Mustahil section, measured at Bur Bitthale near Belet Uen (Cen­tral Somalia), is here described. The succession, dated as Late Aptian to Early-Middle Albian age on the basis of good faunal evidence (Orbitolina texana and Orbitolina sulxoncava), consists of two well developed thickening­coarsening sequences, where four different facies have been recognized. The cap of both sequences is repre­sented by a rudistid framework dominated by Eoradiolites lyratus. We interpret these cycles as shoaling up para­sequences, which are the result of two depositional regressions produced by the progradation of broad shallow­water carbonate systems over the adjacent ramp and deep shelf.