The older formation of the Quaternary period is the Lafayette (also called "Orange-sand" or "stratified drift"), which immediately overlies all the Cretaceous groups except the prairies of the Selma chalk, and all the Tertiary except the Porters Creek and Vicksburg formations and parts of the Jackson.
Nummulitic limestone (Eocene) overlies the Cretaceous in Philistia, and north of Lebanon Eocene and Miocene deposits cover the greater part of the country.
Brick earth overlies it from Kensington to Brentford and west thereof, and appears in Chelsea and Fulham, Hornsey and Stoke Newington, and in patches south of the Thames between Battersea and Richmond.
A deposit of sinter and a calcareous sandstone, known as the Kalahari Kalk, considered by Dr Passarge to be of Miocene age, overlies a sandstone and curious breccia (Botletle Schnichten).
Each escarpment stands forth where a resistant formation overlies a weaker one; each escarpment is separated from the next higher one by a broad step of weaker strata.