From the Upper Jurassic to the Tertiary various transgressions took place
which are responsible for the older marine and the younger continental sedi-
ments which can be found spread as far as southern Egypt today. In the north
they reach a thickness of 4,000 m, while they thin out towards the south.
When the huge block of the Basement Complex of the Nubian Shield was
lifted up, the Late Mesozoic rock layers which consisted mainly of fluvio-
lacustrine deposits in the south were more strongly eroded. Thus the old
folded and metamorphous rocks of the Basement came to the surface in the
present-day Red Sea Mountains. The granite intrusions in the area of Aswan
were exposed and formed the first cataract, which has obstructed navigation
since man has inhabited the area.