LITHOSTRATIGRAPHY OF THE MANGANESE-BEARING UM-BOGMA FORMATION, WEST-CENTRAL SINAI, EGYPT

Detailed investigation of the Lower Carboniferous carbonates of the Um Bogma Formation in 49 surface sections and 45 boreholes in west-centr al Sinai led to the possibility of subdividing this economically impor tant formation into three lithostratigraphic units including from base to top: Ras Samra Member, El Qor Member and Um Shebba Member. These f ormal names are established here for the first time and are described in detail. Strata-bound manganese-iron ores are recorded from the thre e members, but economic deposits are confined to the Ras Samra Member only. The lithologic variations of these members and the stratigraphic distribution of the associated Mn-Fe ores are discussed.