Geology Reference
In-Depth Information
ferruginous patinas could have accumulated at the base of the regolith (see Chapter 3), or near the
source of waters carrying the minerals, namely the small streams flowing in the gutters.
9.6
ROCK DOUGHNUTS
9.6.1
Description
Rock doughnuts are raised rims surrounding rock basins (Fig. 9.20). They have been described
from granitic environments in the Llano of central Texas, and from northwestern Eyre Peninsula,
South Australia, and are also developed in Zimbabwe.
(a)
(b)
Figure 9.20.
(a) Rock doughnut in granite, Enchanted Rock, Llano, central Texas. (b) Rock doughnuts in
granite near Harare, Zimbabwe.
