268 REPORTS OF COMMITTEES. 



have passed over so high a watershed is a very important fact, especially 

 as at present there are no high lands to the south equal to supplying 

 the gravitative force for surmounting such a barrier. 



Before describing the glacial features of this spur and its associated 

 valleys, we must refer to some remarkable features on its south- 

 eastern flanks. What must be regarded as one of the most important 

 discoveries of glaciation in Australia was pointed out to me by Mr. 

 Crossman, in the way of a glacial pavement of great extent and in 

 perfect condition. In approaching this spot from the east, in section 

 196, hundred of Encounter Bay, a deep wash-out creek occurs, exposing 

 banks of morainic material, 20ft. deep. At a bend in a tributary of 

 this creek, a little above the junction (section 194), a granite boulder, 

 measuring 14ft. by 12ft. by 8ft. high, is set in the creek bottom, with 

 an expanding base covered with silt. A little lower down the creek, 

 hard glacial sandstone, very irregularly bedded, forms the bed of the 

 watercourse, and on the right bank of this creek are the exposures of 

 the glacial pavement referred to above. 



The Glacial Pavement is evidently of great extent, as three wash- 

 outs, parallel to each other, and making a united breadth of 100yds., 

 show the polished floor to be at least of that extent. 



The most northerly of these washouts is the most extensive, and 

 exposes several faces which are separated from each other by intervals 

 in which the pavement is replaced by broken rock or obscured by creek 

 material. The highest up face, in this line of washouts, is 4yds. long ; 

 60yds. lower down a second polished face occurs, 5yds. long ; and 

 12yds. farther is the main polished face, 30yds. long. Nothing in the 

 way of glacial polish, striae, and groovings could be more perfect and 

 striking. The markings (whether of striae of microscopic size or fluted 

 grooves a foot wide) all have the same direction, at 280°. That the 

 ice was travelling westerly is proved by the frequent deep digs into the 

 pavement in that direction — like a chisel, cutting and jumping as it is 

 pushed along. The slope of the pavement varies up to 10° in the south- 

 east direction. By the scour of this small creek several large granite 

 boulders up to 6ft. have been freed from the finer morainic material. 



The second washaway, parallel with the preceding, at a few yards 

 distance, has a polished face exposed for 12yds., and shows some very 

 fine shallow and wide grooves, giving the same direction as the pre- 

 ceding reading. 



The third washaway is smaller than the above, and carries the 

 same features. 



One of the most interesting features of these extensive exposures 

 of the polished glacial floor is the evidence of crust movements and 

 slight faulting which have occurred since the ice withdrew from South 

 Australia. In the cases of the large face, in the first washout described, 

 there are six successive and parallel drops of the floor, from 2in. to Sin. 

 in depth, producing a series of small step faults. In the third wash- 

 away there is a normal fault of 15in., the fault plane being from 3in. to 

 4in. wide, and filled with a ferruginous breccia. In all cases the faulting 

 shows a downthrow to the south-east. 



