IN CARBONIFEROUS AND HAWKESBTJRY SEEIES, N. S. WALES. 193 



Most of the stones presented the appearance of having been ground, 

 and showed a dull polish, and many exhibit well-marked striae. 

 The proportion of the boulders possessing the requisite grain, 

 hardness, and durability to receive and preserve delicate ice- 

 scratches was small as compared with the number unfitted for such 

 purpose. Those which are most decidedly striated are dark clay- 

 stones, fine-grained quartzites, and slates. These are scratched on 

 the top, bottom, and sides. The striae, although plainly visible, 

 are not deeply cut, and no grooves were observed. Most of the 

 boulders are partially covered with a thin crust of carbonate of lime, 

 the derivation of which is obvious from the calcareous nature of the 

 shales. The largest specimen of the glaciated blocks exhibited was 

 found by the author firmly bedded in shale at a depth of 15 feet 

 from the surface. The other specimens were also obtained in position. 

 The largest boulders are those of clay -slate, granite, and aplite. 



The following is a list of the different varieties of rocks observed to 

 occur as boulders in the shale : — quartz and felspar-porphyry ; clay- 

 slate ; dark felspar-porphyry or porphyrite ; quartz-felsite, frequently 

 showing fluxion- structure ; quartzite, reddish brown, greenish 

 brown, and dark blue with iron pyrites ; quartz ; black quartz (?) ; 

 coarsely crystalline quartz and felspar-porphyry ; f elsite ; diorite (?) ; 

 claystone ; shale ; felspathic quartzite ; granite ; aplite ; gneissic 

 granite ; chloritic quartz-porphyry ; decomposed vesicular trap and 

 hornblende-schist. 



The nearest parent rock from which some of the boulders could 

 have been derived is about 30 miles distant. 



The largest boulder measures 3 feet x 1 foot 4 inches x 7 inches. 

 The beds have such a fresh appearance that when viewed from a 

 short distance they might easily be mistaken for Pleistocene 

 moraines. No evidence as to their total depth could be obtained 

 at Grass-tree. At Branxton, however, Mr. "Wilkinson roughly 

 estimates their thickness at not less than 1000 feet. 



Fossils were not found by the author in the Grass-tree beds, but 

 there is stratigraphical evidence for correlating them, provisionally, 

 with those at Branxton. 



At present, all that can be truly stated is that, at Branxton, 

 glacial beds exist of undoubted Carboniferous age, and similar beds, 

 presumably of the same age, at Grass-tree. The coarse marine con- 

 glomerates of the lower Coal-measures, near W allerawang in the 

 western coal-field, containing large smooth blocks of Devonian 

 quartzite, are believed by Mr. Wilkinson to be also partly of glacial 

 origin. 



II. Probable Ice-action in the Triassic Hawe:esbttry Series. 



Two phenomena observed in the rocks of the Hawkesbury series 

 appear to indicate that ice was present, to a certain extent, during 

 their deposition. 



These are : — 



f 1. Disrupted angular fragments of shale. 



\ 2. Contemporaneously contorted current-bedding. 



