In a detailed investigation of the lithostratigraphy, biostratigraphy, mineralogy and
geochemistry of the stratigraphic interval spanning the Danian/Selandian (D/S) transition about 16 m
within the Dakhla Shale exposed at Gabal el-Qreiya has been examined and collected. Litho -
stratigraphically, the part of the Gabal el-Qreiya section under investigation is mainly composed
of grey shale and encompasses the D/S boundary. There is a marker bed (~30 cm thick) represents
the D/S boundary at Gabal el-Qreiya that consists of four alternating black and brownish organic-rich
shale bands (~5-12 cm thick each) sandwiched between two thick grey shale beds. We formally
describe this interval as the el-Qreiya Bed, which has been recognized in several localities elsewhere
in Egypt. The sediments of the el-Qreiya Bed are very similar to those in the lower part of the
earliest Eocene Dababiya Beds in Egypt, which include thinly laminated, phosphatic (fish debris),
organic-rich and extremely pyritic shales. The organic debris is noticed as amorphous organic matter
and woody fragments. Biostratigraphically, the succession is subdivided into six planktic foraminiferal
biozones, documenting a case of continuous sedimentation during the D/S transition. These
biozones are: The Danian Praemurica uncinata (P2), Morozovella angulata (P3a) and Igorina
albeari/P. carinata (lower most part of P3b) biozones and the Selandian I. albeari (main part of
P3b) and Globanomalina pseudomenardii (P4a) biozones. The basal surface of the el-Qreiya Bed
is marked by the last appearance of Praemurica carinata (El Naggar) and is taken to mark the
Danian-Selandian boundary. Above the D/S boundary, the planktic foraminiferal taxa of the
praemuricids were gradually replaced by morozovellids, acrininids and igorinids. The clay
mineralogy analysis of these sediments indicates alternating periods of humid (high kaolinite)
and dry (low kaolinite) climatic conditions during the deposition of the el-Qreiya Bed. Geochemical
analyses of samples representing the el-Qreiya Bed and the sediments above and below revealed
that the sediments of the el-Qreiya Bed are characterized by high anomalies in chalcophile elements.
The trace elements are most probably incorporated into the phosphatic components and organic
matter. The sediments around el-Qreiya Bed are normal marine sediments deposited in oxic bottom
waters. The sediments of el-Qreiya Bed reflect anoxic/euxinic marine environments and deposition
in H2S-containing bottom waters rich in organic matter. It is believed that high productivity and
upwelling activity were responsible for such conditions and the sedimentological, mineralogical,
geochemical and faunal characteristics of the D/S boundary at Gabal el-Qreiya section.