This study deals wi th the mineralogy and geochemistry of the mineralogical phases found in the
Beida Shale Member belonging to the Dakhla Formation and exposed at G. Duwi section, Red Sea, Egypt.
The sediments of the upper Dakhla Formation (85 m thick) are composed mainly of grey, dark greyto
black shales as well as grey marly shales and pink marl. These sediments are intercalated by many
thin layers (30-50 cm thick) of brown and reddish brown marl. The marl and marly shale are slightly to
moderately dolomitic.
The stereoscopic microscopy and the SEM survey of the insoluble residues of these sediments have
revealed the presence of Mn-oxides (mainly manganite), dolomite, goethite pseudomorphs (after pyrite
and pyrite framboids), goethite, few Fe-Ti oxides and organic carbon particles. The mineralogical and
geochemical investigations indicate that the manganese oxides, dolomite, goethite and goethite
pseudomorphs are of diagenetic origin. However, the Fe-Ti oxides are of detrital origin. These
mineralogical contents suggest that the Beida Shale Member is a normal marine sediment deposited in
oxygen- containing bottom waters, except for the middle part which is composed of dark grey shale and
contains pyrite and pyrite framboids. This part reflects an euxinic marine environment and deposition in
anoxic, H2S- containing bottom water.
X-ray diffraction analysis of the clay fraction revealed that the sediments under investigation are
composed of detrital kaolinite, smectite and illite. The fluctuation in frequencies of these minerals
within the sediments indicates a warm / humid climate with high rain falls at the K/T boundary and
during the Danian periods as indicated by the abundance of kaolinite. This is followed by a temperate or
cool and dry climatic conditions during the Selandian-lowermost Thanetian and a sea level rise in the
early Thanetian as indicated by the low kaolinite content and the relative abundance of smectite.