530 GEOLOGY AND PETROGRAPHY OP CLAEEXCETOWX-PATERSOX DISTRICT, ii., 



During the course tlirougli the upper portion of the valley, each river shows 

 a distinct parallelism with the dominant strike of the rocks and below the hard 

 bar, i.e., in the lower portion, the effect of differential resistance is minimised 

 (the sediments eroded being the Permo-Carboniferous) and the significance of 

 faulting (e.g., in the case of the lower Williams) is greater. A glance at the 

 map will show that each of these two rivers possesses similar bends where pass- 

 ing through the Patersou toscanite. An examination of the stratigraphical data 

 showed that the toscanite in each of these places is locally thin. One can see 

 that these temporary minima of thickness determined the passage of the rivers 

 which, close by, were controlled bj' the strike, east and west, of the rocks. 



The country separating the rivers is composed of varying units and dis- 

 section is well advanced. The divide between the two drainage systems is, as 

 shown on the contour map (Text-fig. 4), a very narrow one and it is certain 

 that in a short time, geologically speaking, quite a decided rearrangement of the 

 watercourses will take place, as a result of stream piracy between the tributaries 

 of the Williams and Paterson Rivers on the one hand and the several tributaries 

 of the Williams on the other. 



Some of the small tributaries of these two large rivers, which possessed 

 considerable gTade, have aggraded the lower portions of their channels and sub- 

 sequently cut into the resulting boulder beds, producing, as a result of the nature 

 of the rock-units in association, such features as a high ridge and a level plain 

 adjacent to one another. At the mouths of small tributaries, especially in the 

 Valley of the Paterson, fans of boulder deposits are common. 



It is now proposed to describe a number of localities after indicating the 

 nature of the resistance of the various units, thus showing the control exercised 

 by the disposition of the strata. 



The members of the Burindi Series are chiefly non-resistant, as also are the 

 rocks of the Basal Stage of the Kuttung Series. Both these divisions contain 

 a lot of conglomerate, the matrix of which weathers rapidly, large tracts of re- 

 sidual pebbles being found. 



In the Volcanic Stage, the Martin's Creek andesite and the Mt. Gilmore 

 toscanite are the most resistant members, the others only registering medium op- 

 position to erosive forces. Strangely enough, as SussmUch pointed out, the 

 dacites and rhyolites of this Stage are, in general, easily eroded, but this may- be 

 due to their lack of any great thickness. The conglomerates and tuffs are soft 

 units and are more readily excavated than the sandstones, conglomerates, and 

 tuffs of the Glacial Stage, which are of essentially a different composition. The 

 toscanite of the latter Stage is a very resistant member and has had a dominant 

 influence on the topogTaphic evolution. The Main Glacial Beds generally pro- 

 duce mature type of country with lack of definition and are not hard types, while 

 of the basalt, which occurs as cappings only, little can be said regarding corrasion, 

 although chemical weathering has progressed to a considerable degree. 



Thus it is manifest that the topography should, on account of the senile stage 

 not yet having been reached, exhibit a variety of land forms, prevalent among 

 which should be the occurrence of dip-slopes of hard units, and the following 

 short local descriptions will indicate tliis. 



Hilldale District. 



Plilldale village is surrounded by hills chiefly of Kuttung rock, except to the 

 west, while the lower country consists of Burindi beds. This arrangement is due 

 to the erosion of a dome-like mass in the latter beds, the occurrence of the high- 

 land being ipossibly connected with a fault, Fg, but chiefly due to the somewhat 



