266 REPORTS OF COMMITTEES. 



(a mile above Crown Point Cattle Station), described by Mr. J. J. East. / 

 The present writer has called attention to a similar distribution and 

 re-arrangement of the glacial erratics in deposits of recent age in the 

 Hergott and Stuarts Creek districts, g The supposition that the 

 erratics of Yellow Cliff and Cunningham Gap are of Cambrian deriva- 

 tion, if confirmed, places the northerly occurrence of the glacial beds 

 in about 25° 30' south latitude, or within about 2° of the Tropic of 

 Capricorn. As elevation above sea-level cannot in this instance be 

 predicated to explain the occurrence of ice in these low latitudes, the 

 climatic conditions must have been exceptional and extraordinary to 

 admit of floating ice carrying its burden of morainic debris almost 

 into the equatorial belt. 



3. Thickness of the Beds. — The determination of the thickness of 

 the glacial beds is often rendered difficult by stratigraphical disturbances, 

 which, at times, duplicate the outcrops, and at others more or less 

 cut them off. The absence of bedding planes through great thicknesses 

 of unstratified till introduces another element of uncertainty in this 

 particular. In the gorge of the Appila Creek, near Appila-Yarrowie, 

 there is a very clear exposure of the beds with their upper and lower 

 boundaries sharply defined. The measurement in this case is rendered 

 the more easy in that the beds are tilted to within a degree or two of 

 the vertical, so that the width of the outcrop may be taken, practically, 

 as the thickness of the beds. In this instance the thickness amounts 

 in the aggregate to 1,500ft., including 860ft. of characteristic till with 

 boulders. The till proper occurs in two main horizons ; the lower 

 occupies the basal position of the beds and is 750ft. thick ; and the 

 other makes the topmost bed, and is 110ft. in thickness. Between the 

 two beds of till there is a series of gritty quartzites, slates, and a thin 

 limestone, aggregating 640ft. Throughout this middle zone erratics 

 are either absent or rare. In other sections of these beds, as at 

 the Sturt Valley and the Onkaparinga, for example, the barren 

 zone isl of much less extent, and more divided up in its relationship to 

 the till. 



4. Form of Glaciation. — All the evidences available point to floating 

 ice as the agent immediately concerned in producing the deposits 

 under consideration. In no case has a glaciated floor or underlying 

 unconformable series been observed, which might be expected to occur 

 in the case of land ice. The upper and lower limits of the ice deposits 

 are sharply defined, as no erratic occurs either above or below those 

 limits ; but, on the other hand, there is a stratigraphical continuity in 

 the sedimentation which has taken place. It was a soft sandy bottom 

 which received the first contributions of the ice-borne material, a fact 

 which is inconsistent with glacier ice, except in a very limited way. 

 Indeed, the extent of the area affected Hmits the agency either to a 

 continental ice-cap or an oceanic basin, and the evidences favor the 

 latter. At the same time the ice must have floated from an area under- 

 going intense glaciation, which is evident from the enormous amount 



/ Trans. Roy. Soc, S. Aus., vol. XII., 1889, p. 44. 

 g Trans. Roy. Soc, S. Aus., vol. XXX., 1906, p. 330. 



