Geology Reference
In-Depth Information
(a)
(b)
Figure 6.9. (a) The scarp retreat model showing inselbergs as the last remnants surviving on major divides.
(b) Jessen's model of reduction of inselbergs by scarp retreat but with progressive steepening of
slopes.
Such weathering of cor ners or edges of fracture-def ined blocks could tak e place either on
exposed surfaces under attack b y epigene processes or beneath the surf ace, in the g roundwater
zone, as is well illustrated by the formation of corestones (Chapter 5). Those who interpret born-
hardts as remnants of circumdenudation and the rounded form as due to the weathering of exposed
corners and edges b y epigene agencies also constr ue sheet fractures and str uctures as ha ving
formed in response to pressure release and in relation to the shape of the landfor
m (but see
Chapter 2
).
6.3.3
Tectonics and structure: faulting and lithology
Some investigators interpret bornhardts as Härtlinge, monadnocks de résistance or de dureté, that is,
as what many refer to as structural forms
sensu stricto
, or forms due to the exploitation of crustal
weaknesses by external agencies. Several explanations involving the intrinsic characteristics of the
country rock ha ve been of fered for bor nhardts standing abo ve the adjacent plains. Basicall y,
