These rocks are our starting point, respecting which there is no evidence of their age, or even relative age.
(4) We now come to a long period of denudation of the Atlas ridge, and its sculpturing into hill-and-valley contour, before the deposition of the Red Sandstone and Limestone series.
(5) The deposition over what is now the Marocco plain, of the Cretaceous Red Sandstone and Limestone series (and beds possibly of Miocene age), which also occupies pre-existing valleys in the older porphyrites of the Atlas.
(6) The intrusion of diorite into the porphyrites and porphyritic tuffs, probably accompanied by a further elevation of the Atlas range, disturbing the stratified Red Sandstone and Limestone series, throwing them into a synclinal trough, from which the beds rise northwards towards the plain, and southwards towards the Atlas.
(7) A further long period of denudation of the Red Sandstone and Limestone series, rescooping out the lateral valleys of the Atlas, in continuation of the valleys that existed in the porphyrite ridge prior to their deposition, and also denuding the beds in the Marocco plain to the extent of at least 300 feet, leaving isolated remnants as flat tabular hills rising above the present general level of the plain.
(8) A further possible emission of red porphyrites through the stratified beds of the plain, which may have been contemporaneous with the eruption of the red porphyry dykes of Djebel Tezah, in the High Atlas; but I could not clearly ascertain whether these bosses really pierced the stratified beds, or were existing before their deposition.
SKETCH ACROSS PLAIN OF MAROCCO TO WATERSHED OF GREAT ATLAS
(Note The Camels Back Hills & Frouga are West of the back of section)