81 



level, and the great escarpment at the Parachilna Gorge is 

 probably 1,000 ft. higher than the railway. 



The quaquaversal dip of the beds around the apical 

 portion of the dome is fairly consistent as to direction, but 

 varies much in the angle of dip. The Archaeocyathinae lime- 

 stones represent the highest exposed horizon on the western 

 side, the beds in superior position having been thrown down 

 by the great north and south fault, and have become obscured 

 by recent alluvia and blown sand. From the gorge on the 

 'west to Blinman, a distance of about 10 miles, the prevailing 

 dip is westerly. From Blinman to the Archaeocyathinae beds 

 at the old Wirrealpa station, on the east, at a similar distance 

 of about 10 miles, the prevailing dip is easterly. At about 

 the same distance to the northward of Blinman is Patawarta 

 Hill, which probably represents the thick quartzites that 

 underlie the Archaeocyathinae limestones at the Parachilna 

 Gorge, and, if so, those fossiliferous limestones might be 

 expected to occur on its northern slopes. 



A 10-mile section of rocks that lie in one direction, at a 

 fairly high angle of dip, would make a very thick series, and 

 suggests the possibility of faulting along the strike that might 

 cause a repetition of the beds and give a fictitious appearance 

 as to their thickness. Minor faults were recognized in several 

 places, but nothing came under my observation that looked 

 like a repetition of the beds on a large scale, although in a 

 single traverse such an occurrence might easily be overlooked. 



One of the features of the district is the great amount of 

 crush-rock that is developed, at intervals, over scores of square 

 miles. This class of rock takes all the forms usually developed 

 under such conditions, viz., crush-breccia, crush-conglomerate, 

 over-riding, and sometimes telescoping, when the shales and 

 dolomites interpenetrate one another. Some of the purple 

 shales are, in places, crushed into a confused mass in which 

 signs of bedding can only be recognized in disconnected frag- 

 ments. These features are, perhaps, in greatest evidence 

 where the igneous rocks are in close proximity. The only 

 locality where I have noticed autoclastic phenomena in any 

 degree comparable to this is along the flanks of the great horst 

 that forms Mount Remarkable (see Howchin, ' ''Geology of 

 Mount Remarkable, " Roy. Soc. S. Austr., xL, 1916, p. 545). 

 In the latter case the crush-rock has been caused by vertical 

 faulting on a large scale; in the northern Flinders Ranges, 

 lateral faulting, by a sliding horizontal motion, has been of 

 common occurrence, and would, probably, be more potential 

 in causing "crush" than vertical movements. 



The beds above the horizon of the Archaeocyathinae lime- 

 stone, which outcrop near the Wirrealpa Station and in the 

 upper part of the Balcoracana Creek, are the highest members 



