164 



cutting, near Dinglebedinga School, in the south-western por- 

 tion of the area. This boulder was accepted as glacial by 

 Prof. Howchin, into whose charge it was given. Is this a 

 fluvio-glacial deposit of Permo-Carboniferous age, or is it a 

 Tertiary bed composed, in part, of redistributed glacial ? If 

 the latter, did it come from the glacial deposits of the Finniss 

 River, to the south ? This would mean a reversal in direction 

 of the present drainage. It is much more probable that the 

 glacial deposits of the south, though extensive, are neverthe- 

 less a small remnant of a sheet of material which once extended 

 much farther north, and the Meadows Valley may, in part, 

 be a trough the earliest features of which were due to glacial 

 erosion in Permo-Carboniferous times — a much more imperfect 

 example of "fossil glacial topography," however, than that 

 of the Finniss River district, described by Prof. Howchin, 

 where erosion has laid bare a portion of an ancient landscape 

 with remarkable precision. 



What, then, is the past geographical history of this 

 region ? Briefly it appears to be as follows : — The Meadows 

 Valley is regarded as a small dismembered portion of an ancient 

 north and south stream the southern course of which, beyond 

 the area under consideration, has not been traced but indica- 

 tions of it might be expected in the direction of Myponga Creek. 



a 



This valley existed before the uplift of the present high- 

 lands, and in the Meadows Creek section there is some pro- 

 bability that its course coincided with a much more ancient 

 glacial valley partly filled with till. 



Peneplanation advanced to a mature stage with conse- 

 quent aggregation and filling up of the old valleys, resulting 

 in the formation of an extensive piedmont plain over which 

 the streams flowed independently of the underlying structure. 

 Early subsidences and warping may have assisted in the insti- 

 tution of the diagonal direction of drainage, as shown by the 

 present positions of the Torrens and Onkaparin^a. Fault 

 block dislocation followed, with the gradual establishment of 

 the present distribution of highland and plain, giving rise 

 to a revived erosion cycle and the entrenching of the deeply- 

 cut river valley into the rising segments. The existing cycle 

 is one of discordances of level and active erosion along the 

 fault scarps, providing short, steep, actively-eroding streams 

 tending to cut back into the old topography and divert 

 remnants of the old north and south valleys into steep-graded 

 easterly or westerly flowing streams. 



The north and south strike ridges of hard rock delayed 

 this process, but weak places were eventually found. Tlie most 

 important of these was the southern continuation of the Bull 



