72 Notes on the Geology of the Country around Goulbum. 



the proximity of limestone. The association of limestone and 

 oxide of iron is invariable throughout this county. Massive 

 ironstone is of common orcurrence along many alluvial water- 

 courses. But the accumulation most interesting geologically is 

 the ironstone breccia which covers the slate country between 

 Bungonia and the Shoalhaven, as well as other parts. It con- 

 sists of angular fragments of slate, cemented by oxide of iron 

 into a hard mass. It attains a thickness often exceeding 30 feet, 

 and has been eroded into hills And valleys. It is very conspicuous 

 along the Washedaway Creek, (a tributary of the Shoalhaven, 

 east of Bungonia), and there overlies a thick accumulation of 

 alluvial deposits. A miner's shaft sunk in a slight valley, sur- 

 rounded on all sides by " made hills" of this conglomerate, 

 passed through the following : — 



Feet. 

 Soil and clay ... ... ... ... ... ... 13 



Ironstone conglomerate, consisting of quartz and oxide of 



iron ... ... ... ... ... ... 2 



Pipe clay, stratified, containing in lowest stratum fossil 



leaves and bones ... ... ... ... ... 75 



Auriferous gravel, pebbles one to two inches diameter 12 



Total 102 



Quartzite and slate bottom. 



The same kind of ferruginous breccia as that just described is 

 also met with in Pegar Gully, a small tributary from Mount 

 Wayo to the Wollondilly. 



There are caves in the limestone on the Shoalhaven, but 

 whether they contain any deposits of interest has not been 

 investigated. 



The districts of Oallen and Nadgigomar are largely covered 

 with loose sand and gravel. 



The only other fact to which I would allude is the remarkable 

 occurrence of huge granite Doulders at several points along the 

 Boro Creek, when no such rock can be discovered anywhere in 

 the surrounding neighbourhood. One of the largest of these 

 blocks observed was rudely spherical, and had a diameter of 15 

 feet, and must have weighed about 128 tons. The only known 

 means hy which such huge masses become transported to a 

 distance from their parent rock, is that of ice. The blocks, 

 however, do not exhibit any of the characteristic markings of 

 ice action, such as polishing grooves, or scratches ; nor are 

 there any other deposits elsewhere, which could be safely said to 

 possess a glacial origin. 



