Geology Reference
In-Depth Information
Figure 4.13.
The Springbok Flats, a subdued but gently rolling plain, north of Pretoria and in Northern
Province in South Africa.
Figure 4.14.
Very flat plains in granite and gneiss, Meekatharra, Western Australia.
These flat plains are either etch surfaces reduced to extraordinary low relief by long continued
subsurface moisture attack, or they represent the ultimate stage of planation, the possibility of which
was appreciated by Davis (1909) and by Peel (1941). Such flat plains are most likely to evolve in
areas of tectonic stability and to be preserved in areas of arid climate. The examples cited are
located in arid and semi-arid areas of Africa and Australia (Williams, 1969) and in shield areas that
have suffered little tectonic disturbance since the middle Proterozoic or even earlier, for over wide
areas of both of these continents Upper, and even Middle, Proterozoic strata remain essentially
undisturbed.
4.5
MULTICYCLIC AND STEPPED ASSEMBLAGES
Multicyclic forms are developed in granitic terrain as a result of the relative lowering of baselevel,
stream rejuvenation and landscape revival. The plains become high plains, located high in the
relief, as in the Sierra Nevada, in the Rocky Mountains of Colorado and Wyoming (the Sherman
Surface) (Mackin, 1937, 1970); on Dartmoor; in the Ávila-Villacastín region of central Spain and
throughout in the northwest of the Iberian Peninsula; in several parts of southern Africa and elsewhere.
