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niferal white chalk (Danian) 60 to 100 metres thick, especially developed in tne 
region of the oases to the west of the Nile. 
The Nubian Sandstone, the oldest sedimentary deposit in Egypt, occupies a 
very large area, especially in the south; wherever its base is exposed and has 
been critically examined, the sandstone is found to be laid on to the denuded 
surface of the underlying crystalline rocks. Thinner argillaceous bands are 
almost everywhere associated with the sandstones and the latter vary much in 
colour, texture, and hardness. In its widest sense the term “Nubian Sandstone” 
includes deposits of much greater age than Upper Cretaceous, undoubted Carbo- 
niferous fossils having been detected in some localities. The formation must be 
regarded as representing the slow accumulation of sediment in immense inland 
lakes during a great lapse of time. Although temporary marine invasions left 
their mark at intervals, it was not until the Cenomanian that continued depression 
caused a steady recession of the shore line from north to south, so that in 
Senonian times practically the whole of the country was occupied by the 
Cretaceous sea. 
North of Silsila in the Nile valley the sandstones gradually give way to a 
series of flaggy ripple-marked sandstones alternating with sandy shales and 
clays, at the top of which are beds rich in bones and coprolites of fish, associated 
with hard oyster-limestones, overlain in Wadi Hammama, E.-N.-E. of Qena, by 
a limestone containing abundant remains of cephalopoda; these beds are of Upper 
Senonian (Campanian) age. East of Sabaia, in the Nile valley, they are followed 
by a 200 metre series of finely laminated clays, Separated by bands of marly 
limestone, the greater part of which is of Cretaceous age and liomotaxial with the 
Exogyra clays and white chalk (of Campanian — Danian age) which in the 
southern oases follow on the rich bonebeds overlying the Nubian Sandstone. 
Anterior to and during the deposition of these clayey beds in the south, thick 
accumulations of limestone were being formed in the more open sea to the north 
and are visible to-day in the Cretaceous area of Abu Roash near the pyramids 
of Giza, (and to a lesser extent in Jebel Shebrewet on the Gulf of Suez), where a 
great complex of limestones of Turonian and Senonian ages occurs. Finally a 
deep sea deposit of white chalk forms the summit of the Cretaceous throughout 
the Western Desert. 
49. Eocene. Our knowledge of the junction of the Cretaceous and Eocene in 
several parts of the country leaves much to be desired. Where the Eocene is 
most fully developed its basal member consists of a group of green argillaceous 
deposits, known as the Esna shales, well seen at the base of the cliffs throughout 
the Esna-Qena reach of the valley. These beds everywhere pass conformably 
upwards into the Lower Eocene (Libyan) limestones above, but in the Nile Valley 
and the Eastern Desert the exact line of demarcation between them and the 
lithologically similar Cretaceous clays below is still somewhat obscure. In Kharga 
and Farafra they form a well-marked band between the White Chalk (and 
associated clays) at the top of the Cretaceous and the Libyan limestone of the 
Lower Eocene. The Esna shales may in fact be regarded as passage beds, and 
where they exist appear to bridge over the lapse of time which is represented by 
a decided unconformity between the Cretaceous and Eocene in the north of the 
country, as in Baharia Oasis and at Abu JEtoash. 
