239 



the hills, the explanation of which may be that the strong 

 and prevailing westerly winds have a tendency to bare the 

 ground on the exposed side, whilst the wind - driven sand 

 gathers on the eastern or lee side of the hills. 



(c) The Giles Ceeek and River Finniss Glacial Basin. 



Physio graphical. — The glacial basin of the Finniss is situ- 

 ated to the north-east of the Mount Compass and Nang- 

 kita basin, and is continuous with it. It includes, in addi- 

 tion to the main valley of the River Finniss, the lower portion 

 of Bull's Creek from the point where it emerges from the 

 Bull's Creek Ranges; and the still more important Giles Creek, 

 which flows through glacial sandstones throughout almost its 

 entire course, forming a junction with the River Finniss above 

 Queen's Own Town. 



The basin is surrounded by hills of Cambrian slates and 

 quartzites rinding their greater elevations in the Mount Mag- 

 nificent and Bull's Creek Ranges, Gemmell's Hill, Giles Hill,, 

 and lesser heights near Strathalbyn. A ridge of old rocks, 

 with Morphett's Hill and Mount Observation as principal 

 heights, occupy the centre of the basin, and is entirely sur- 

 rounded by glacial beds. The basin is open to the south- 

 east, where it presents a wide front to the Murray flats, and 

 the glacial beds become obscured in that direction by newer 

 deposits. 



The River Finniss has already been described as taking 

 its rise on the flat and sandy watershed between Mount Com- 

 pass and the Willunga Range. As this wide valley is occu- 

 pied by glacial deposits, it is probable that it represents 

 surface features that were contemporaneous with those de- 

 posits. It is a good example of physiographical unconformity, 

 for it is clear that the existing streams have played no part 

 in excavating the primary valley. 



The River Finniss pursues a very erratic course. It first 

 forms a loop, doubling upon itself, and then flows easterly 

 along the base of the Mount Magnificent Range with glacial 

 country on its southern side. On entering the Hundred of 

 Kondoparinga it takes a northerly course, following the base 

 of the same range till within a mile of Ashbourne, where it 

 turns sharply to the east and, forsaking the valley, cuts a 

 deep gorge through the old rocks of the Mount Observation 

 Range and at right angles to the range. Instead of going 

 through this ridge of hard rock into the soft country beyond, 

 it turns due south again and pursues a very tortuous course 

 down the centre of the ridge, until, nearing Mount Observa- 

 tion at the southern end of the ridge, it becomes directed 

 to the south-east and flows past Queen's Own Town into the 



