Chapter IV: Section XII: Pliocene

J.—_Marine deposits: Middle Pliocene._—Marine deposits of
Sidmant with typical Middle Pliocene mollusca. Relation of
these deposits to the gravel terraces as yet unknown though
important 71

K.—_Borings on Rock Surfaces; of doubtful age._—Apparently
due to marine boring mollusca. No exact evidence as to age.
(α) Low level borings from zero to 20 metres above sea-level.
(β) High level borings at 112 metres above sea-level. Limited
occurrences of borings 71

L.—_Gravel Terraces:? Upper Pliocene._—Well marked terraces
of gravel up to 170-180 metres above sea-level. East of Sêla.
Character of deposit. East of Sersena and Roda. N.N.E. of
Tamia, N.N.E. of Garat el Faras, east and north-east of Garat
el Gindi. Relation to different series. Character of gravels
at Elwat Hialla. West of Elwat Hialla gravel terraces almost
completely removed by denudation. Traces near Widan el Faras
and near Garat el Esh. Height of terraces in latter locality
determined as 170 metres above sea-level. Terrace marks shore
line of great sheet of water, whether freshwater or marine.
The great plains of the Fayûm possibly in part plains of marine
denudation 73

M.—_Gypseous Deposits: probably dating from the close of the
Pliocene._—Extension in Nile Valley and Fayûm. Section at
Medum. On the east side of the Fayûm. Gypsum cemented
conglomerate. Close connection with upper part of gravel
terraces 77

N.—_Summary of Pliocene Period_ 78

SECTION XIII.—PLEISTOCENE—

Earliest existence of a freshwater lake. Probably not a
remnant of the Pliocene sea or lake in which gravel terraces
were formed. Intermediate denudation of area. Date of earliest
entry of Nile waters doubtful. Freshwater lake of Nile Valley.
Drainage down the Nile Valley and establishment of river.
Breaking down of gravel ridge separating the valley and the
Fayûm. Entrance of flood waters. Formation of lake and
deposition of sediment. Subsequent disconnection of Nile Valley
and Fayûm owing to erosion of river bed. Rise of Nile in
prehistoric and historic times. Reconnection. Geological
evidence for the existence of great freshwater Pleistocene
lake. Position and dimensions. Fossil fauna of the lake, and
its difference from all other Egyptian faunas. Blanckenhorn’s
conclusions 79