The Geology and Physiography of the Gosnells Area. 
247 
As maturo valleys were ])Vodueed in the first cycles more time must have 
passed between the two movements than has passed since the last uplift. But 
until we have more quantitative data of the rate of erosion of the local 
granite, we cannot suggest the absolute age of either movement. 
C. Streams. 
None of the streams draining the area can be described as the ‘bnajoP^ 
stream. Most of them are short, flow due west down the scarp and may be 
explained as consequent on uplift of the peneplain. Jutson (1934, p. 1(19 and 
tlg'ure p. 171) states that the initial drainage of the elevated peneplain was 
to the south-east. Traces of a south-easterly <lrainage (now reversed so that 
the streams flow norlh-west) are found in the north-eastern corner of the 
country mapped. Generally, the noilhern sides of the valleys of streams 
flowing west are steeper than the southern. 
Kills Brook rises in the highest jjart of the area and Hows a little to the 
north of west. It cuts through the ({uartz “blow’’ at one of its thinnest and 
weakest points: in this way its course has been determined by geological 
structure. 
The course of sti-eam B is more complex than that of the other young, 
westerly-flowing streams. It Hows due west for most of its course, but for 
about 250 yards it runs a little to the west of north, parallel to the major 
joint-direction of the surrounding granite. Its tributary stream C has cap- 
tured the head waters of stream 1), and a wide, shallow wind-gap now separ- 
ates the pirate and the beheaded streams. 
D. Femnmits of the 'J^ene 2 ^lain. 
High, laterite-covered country of faint relief extends over most of the 
eastern part of the area. It has already been mentioned (under “General 
Features”) that the peneplain (or, as it is now, the plateau) has been very 
completely jireserved outside the Gosnells area. 
K. Effect of Geology on Topography. 
The different geological formations are uneciually resistant to erosion. 
The quartz masses, by far the most resistant, stand up as isolated hills and 
occupy the crests of ridges. Basic dykes, as they are so much softer, cannot 
easily be traced through the quarlz “blow”— in a short visit one may gain 
the impr(‘Ssion that the quartz “l)i(tw” does cut the dykes. But though they 
are marked by dejn'essions whore they cut the quartz ridge, the dykes may 
be followed through the quartz by isolated boulders and red soil. 
Generally the basic dykes are the most resistant of the other rocks; 
followed by granite, and lastly sediments (qnailzite, conglomerate and shale 
in order). The edge of the laterite plateau may somelimes be marked hy a 
breakaway, capping a steep scarp up to 30 feet high, but more often both 
breakaway and scarp ai'e absent. 
F. Springs. 
In many places just below the laterite level, patches of greener vegeta- 
tion mark the site of water seepages. Ho great is the amount of water which 
percolates through the laterite that Wright Brook and streams B and C are- 
perennial. The only “spring” which does not issue from beneath the laterite 
is a small one by the side of a dyke in the quartz “blow,” seven chains north- 
east of the Mountain Quarry. It Hows only in the winter months. 
