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deposits form a highly characteristic till — unstratified, with 

 a ground mass more or less gritty. The beds are coarsely 

 cleaved, with flaky surfaces in the direction of the cleavage, 

 and producing, on weathering, rough serrated outcrops. The 

 grain varies in the degree of siliceous cement, from an earthy 

 mud-stone to a hard quartzitic base. The till includes 

 erratics, promiscuously distributed, and up to eleven feet or 

 more in diameter. Many of these erratics nave no known 

 location of parent rock in South Australia. It sometimes 

 passes into a quartzite or coarse grit, with irregular boun- 

 daries. In most localities the till is, at certain horizons, 

 interstratified with regularly bedded slaty zones, laminated, 

 and destitute of erratics, and not infrequently with thin dolo- 

 mitic limestones, which are generally gritty, and ma-y contain 

 erratics. 



In common with most of the Mount Lofty Ranges, the 

 beds give evidence of pressure and strain. The tectonic 

 forces, operating from the east, have thrown the Mount Lofty 

 beds into great north and south folds, which often develop 

 into overfolds. The effects produced on the till by such 

 pressure are strongly evident and very interesting. The in- 

 cluded erratics, for example, have been forced to assume a 

 position with their longer axis parallel to the planes of cleav- 

 age, whilst the fracture of a great many of these included 

 stones in parallel lines across their short diameters, gives evi- 

 dence of strain operating along the cleavage planes. The ef- 

 fects of such strain are further seen by the apparent distor- 

 tion of some of these stones, and by the presence of fine par- 

 allel strise on their surfaces, caused by rotation in their bed. 

 Striae thus caused are of a totall}^ different kind from glacial 

 striae, and cannot well be confounded with the latter. 



The dip of the beds varies greatly. In some of the north- 

 ern areas, as at Orroroo and some parts of the Flinders 

 Ranges, they exhibit anticlinal and synclinal foldings in large 

 curves. At Petersburg, Appila Creek Gorge, and other places 

 they are practically vertical. In the Sturt Valley they dip 

 under the Tapley's Hill slates at a low angle, whilst on their 

 eastern side they are reversed. In the Onkaparinga Valley 

 they override the newer Tapley's Hill slates. 



The glacial origin of the beds is determined — (n) by the 

 typical features of the unstratified till: (h) the number, 

 great size, and promiscuous distribution of the boulders; (c) 

 the essentially foreign character of the included erratics; (rl) 

 the clear proof of glaciation on subangular erratics : fe) other 

 minor features usually present in ice-laid material. 



Form of Glncintion. — Mr. AVoodward's suggestion of 



