Striated Boulders near Shoalhaven River. 59 



grooving and striation on the underside ; the others were so 

 coated with oxide of iron, that any tine markings which may 

 have been present were completely masked. 



One of the best specimens consisted of a block of quartzite, 

 which before removal measured over 12 inches along its greatest 

 length ; the top side was rough and irregular and it was rather 

 badly jointed, so that it broke into several pieces on being 

 chiselled out. The under side was polished, grooved and tinely 

 striated, while several of the sides were faced and imperfectly 

 smoothed. 



Further south again at Jervis Bay, in the neighbourhood of 

 the small township of Huskisson similar beds occur, but the 

 boulders were not so numerous and none of the few examined 

 showed striation. Some large granitic blocks however were 

 observed resting on the marine platforn), and though these were 

 not embedded they had evidently weathered out of the beds, for 

 similar rocks of smaller size were seen I'/t situ. The largest of 

 these loose boulders measured, roughly, about 6 feet by 2 feet 

 by li feet. The rocks here are fossiliferous, several spirifers, 

 and a Platychisma being collected. 



In 1861, somewhat similar features in rocks at WoUongong 

 were described by the late Dr. T. Oldham^, and the beds were 

 compared with conglomerates in the Indian Talchir series, but no 

 striated boulders were recorded, nor was ice-action suggested at 

 the time to explain the origin of the formation. Later, however, 

 the glacial origin of the Talchir beds was more fully worked out, 

 and in 1885, Mr. R. D. Oldham,^ A.R.S.M., of the Geological 

 Survey of India, examined the New South Wales coal-bearing 

 beds ; he established the glacial origin of the conglomerates at 

 Branxton, WoUongong and elsewhere, and confirmed the correct- 

 ness of the previous correlation of the Australian Permo- 

 Carboniferous beds with the Indian coal-bearing series and their 

 associated boulder beds. 



It appears then, that the presence of striated boulders in the 

 beds at Crookhaven affords further evidence of the prevalence, 

 in Permo-Carboniferous seas even in low latitudes, of floating 

 ice, which, as it melted, dropped its load of stones on the muddy 

 sea floor. 



1 Mem. Geol. Survey of India, vol. iii., p. 209. 



2 Record Geol. Survey of India, vol. xix., pt. i., p. 44. 



