Geology, Petrology and Radioactive Potentiality of Um Bogma Formation in the Area West of Wadi El-Nasab, Southwestern Sinai, Egypt

Abstract

The exposed rocks in Talet Seleim area are represented by the Precambrian Basement Complex overlain by a succession of the Lower Carboniferous Um Bogma Formation and the unconformably overlying Abu Thora Formation. The detailed study of ten stratigraphic sections of Um Bogma Formation revealed that it consists of argillaceous and carbonate rocks. The formation could be subdivided into a lower siltstone-dolostone member, a middle siltstone-mudstone-dolostone member and an upper dolostone member. These rock units have unconformable relationships in several sites and vary in thickness and some lithologic characteristics throughout Talet Seleim area. Their rocks display several primary structures the most common of which are various types of bedding, lamination and biogenic features. Also, the succession is affected by secondary structures such as faulting, jointing and folding and contains gypsum veins and clastic dykes. The petrographic characteristics of the argillaceous and carbonate rocks of Um Bogma Formation vary markedly among its three members. These rocks consist of a large mineral assemblage made up of clay and nonclay minerals; the latter are represented by non-radioactive, radioactive and REEs- and heavy metals- bearing minerals. The existence of some accessory minerals is limited to rocks of certain members and specific parts of Talet Seleim area. The various mineral species occur in a variety of forms, habits and modes of occurrence suggestive of primary-secondary and allogenic-authigenic origin.