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