Geology Reference
In-Depth Information
7
Other granitic residuals and uplands
Though bornhardts are a common, and, it is argued, basic granitic form, other residuals are also
well developed. Some are small, but others take the form of massifs, of which, however, born-
hardts and other forms are the basic component, and some of which, viewed regionally, are them-
selves inselbergs.
7.1
ISOLATED RESIDUALS
7.1.1
Nubbins
Nubbins are hills strewn with blocks or boulders (Figs 1.2c and 7.1). Overall, they are roughly dom-
ical, though some are bevelled. Nubbins are particularly common and well-developed in the trop-
ical monsoon lands, especially South East Asia, where they are the characteristic granite upland.
They are also found in monsoon lands with a distinct dry season, as in northern Australia, and in
areas which experience warm humid seasons such as the Serra da Estrela of central Portugal.
Where nubbin landscapes are found outside the humid tropics, they denote either inheritance from
a former humid climate as in the Mojave Desert (Oberlander, 1972) and other parts of southern
California, or local wet sites, as for instance, in the intermontane ranges near Alice Springs, central
Australia, and in the Llano of central Texas. They are developed in valley floors in the Swakoprivier
valley, south of Karibib in central Namibia (
Fig. 7.2)
,
and the White River valley of Mpumalanga.
Where nubbins and bornhardts are found side-by-side, as, for instance, in the western Pilbara,
Western Australia, the two types are found to be constructed of apparently the same bedrock, so
Figure 7.1.
Granite nubbin in the western Pilbara of Western Australia.
