Integrated sedimentological studies, sequential analysis and clay mineralogy on the lower Eocene rocks
in the Western Desert provided important information on the reconstruction of the depositional basin,
cyclicity, and paleoclimatic conditions. Two formations are recognized; the Esna and Farafra formations,
with a gradational contact in-between. The studied sequence exhibits lateral facies changes as revealed
from field and microfacies investigations. Eight facies were recognized and summarized in a carbonate
ramp model. It represents also a general regressive trend, which records a transition from an outer ramp
into a peritidal zone. The facies stacking patterns constitute several kinds of meter-scale, shallowingupward
cycles. Two different types of depositional cycles are here defined. The stratigraphic sections
show a hierarchical organization of many cycles defined by five depositional sequences. It is suggested
that composite eustatic sea level oscillations caused by cyclic perturbations of the Earth’s orbit played
a fundamental role in determining the formation of the observed hierarchical cyclic organization. Summing
up, it is believed that the paleotopography had resulted from the impact of the Syrian Arc Folding
System. A confusing additional complication is introduced by syndepositional sedimentary structures,
especially during the late Cretaceous/Eocene times, coupled by several tensional forces. Clay mineralogy
has revealed the presence of smectite, kaolinite and illite. Their origin may be attributed to the gradual
increase in the amount of erosion of the newly elevated crystalline source rocks to the south of Egypt, in
areas of moderate rainfall and rapid weathering and/or to reworking processes of soils which presumably
developed on basement rocks. Changes in source rocks or climatic influence during the early Eocene may
account for the observed differences in clay mineral abundances.