Page 157 - Fundamentals of Geomorphology

140 STRUCTURE

a
() Karumba ()
b
River Deniliquin
Wa cool Flinder
s

Cadell River
Cadell
tiltblock
tilt
block
River
Murray
M urray
Broken
River
Creek
Cloncurry
Echuca
River Bama Goulburn
Sandhills
upwarp
upwarp
Selwyn
Selwyn
Campaspe
River
20 km
Diamantin aR.

100 km
Over 200 m
Figure 5.20 River diversions in Australia. (a) The diversion of the Murray River near Echuca, Victoria. (b) The diversion
of the Diamantina River, north Queensland, owing to the Selwyn Upwarp.
Source: After Twidale and Campbell (1993, 80, 346)

(Figure 5.21). The present radial drainage pattern is a flowing around the snout of a plunging anticline, for
response to the doming of Carboniferous, and possi- example, may erode down a few hundred metres and be
bly Cretaceous, limestones. The streams cut through held up by a harder formation (Figure 5.22). The stream
the base of the Carboniferous limestone and into the may then be diverted or, if it is powerful enough, incise
underlying Palaeozoic folded metamorphic rock and a gorge in the resistant strata and form a breached snout.
granite. The radial drainage pattern has endured on the
much-deformed structure of the bedrock over which the
streams now flow, and is anomalous with respect to their LANDFORMS ASSOCIATED WITH
Palaeozoic base. FAULTS AND JOINTS

Persistent rivers Faults and joints are the two major types of fracture found
in rocks. A fault is a fracture along which movement
Streams adjusted to a particular structure may, on down- associated with an earthquake has taken place, one side of
cutting, meet a different structure. A strike stream the fault moving differentially to the other side. They are