Appraisal for the environment, weathering and provenance of Upper Cretaceous-Lower Tertiary shales, Western Desert, Egypt

of shales is considered a key to decipher their environment
evolution, weathering, climatic conditions, and provenance. The
Upper Cretaceous-Lower Tertiary succession is extensively
dispersed in Egypt. The present work is devoted to studying the
Dakhla shales of (Maastrichtian- Danian), Duwi (Campanian) and
Quseir (pre-Campanian) formations. Chemical and mineralogical
analyses were conducted by using seven representative surface
sections from Dakhla Oasis. Dakhla shales are dominates by
Smectite and kaolinite. The average percentages of SiO2, Al2O3,
CaO, MgO, Na2O and K2O are subordinate values. In contrast,
Al2O3 contents of Dakhla shale, TiO2, P2O5 and Fe2O3, contents are
relatively higher than common shale composition. The CIA and
CIW high values due to clay minerals and the absence of feldspars.
This is also confirmed by the smectite domination and subordinate
kaolinite in these formations. The ICV values for Dakhla and Duwi
shales are 0.59 and 0.74 (ICV < 1). The shale is mature and
deposited in a quiescent environment. Whereas the ICV for Quseir
shale is 1.24, it can be incidental that it is immature. The shale is
wholly detrital and a product of moderate to intensive weathering.
The provenance was constituted of granitic and basaltic source
rocks, and the parent provenance is basalt. Consequently, the shale
is deposited under fluvio-marine environments, and the prevailed
condition was of alkaline chemical affinity probably passed through
different environments varying from a fluvial, eolian and shallow
marine.