68 



On Evidences of Glaciation in Central 

 Australia. 



By Professor Ralph Tate. 



[Read June 1, 1897.] 



In the " Geology of the Horn Expedition," vol. II., p. 72, 

 there is described a section of Yellow Cliff, at the south-east 

 bend of the River Finke, near Crown Point Head Station. The 

 chief feature presented by that section is the tumultuously- 

 bedded material, many of the included pebbles, which range up 

 to two feet cube, are standing on end, some of the pebbles are, 

 moreover, sub-angular, smooth, and striated. When on the out- 

 ward journey, this section was closely studied, and partly in the 

 company of Professor Spencer,* to whom I announced my opinion 

 that some of the pebbles evidenced glaciation. However, as I 

 failed to recognise any similar signs of glaciation or co-ordinate 

 phenomenon during the rest of our exploration, I, on my return 

 to Yellow Cliff, and after a brief re-examination of the pebbles, 

 attributed the striation of the pebbles to bedding-lines. 



Professor Spencer, during the early part of this year, collected 

 pebbles from this section, which Professor David informs me are 

 undoubtedly glaciated, and thus confirms my first impression as 

 to the nature of their surface-sculpture. 



The occurrence of large boulders on the north side of Cun- 

 ningham Gap, described by East (Trans. Roy. Soc, vol. XII., p. 

 44), may therefore be explained as ice-borne. 



Date of Glaciation. — Cunningham Gap is a short north and 

 south transverse gorge in a mural line of cliff, which is consti- 

 tuted of the following strata, as determined by me in the tabular 

 mass cf it known as Crown Point: — "Desert Sandstone" in 

 three horizontal bands, about 50 feet, resting on false-bedded 

 friable felspathic sandstone and purple hard sandy clays dipping 

 south at about 50°. These latter are probably decomposed 

 Archaean-rocks, such as those described by East (op. cit., p. 45) 

 at Polly Springs, about 20 miles to the north. 



The formation of Cunningham Gap is of course posterior to the 

 deposition of the Desert Sandstone and its subsequent structural 

 alteration, and thus inferentially is that of the accumulation of 

 the glacial-debris at Yellow Cliff. Moreover, pebbles of Desert 

 Sandstone occur in large proportion in the debris, and these are 

 readily distinguishable from the Ordovician quartzites or the 

 Archaean glassy quartzites which occur in the Macdonnell 

 Ranges. 



* My coadjutor, Mr. A. Watt, in the Department of Geology, had not 

 the opportunity of studying this section. 



