578 GREAT SERPENTINE BELT OF NEW SOUTH WALES, ii., 



and may be traced northwards on to the roadway. This is of 

 considerable width, the spilite being split into several layers, and 

 intercalated with banded chert. 



No evidence of pillow-structure has yet been seen among these 

 rocks, but certainly it was not looked for specially. 



(e). Upper Botvling Alley Tuffs and Breccias. — The Upper 

 Tuffs and Breccias complete the Bowling Alley Series, and occur 

 throughout, from north to south. They are about 3,300 feet in 

 thickness, and are fairly free from intrusions of dolerite and 

 flows of spilite. Interbedded with them, are minor bands of 

 radiolarian clayshales; and probably the western limestone-lenses 

 north of Cann's Plains and Hyde's Creek, belong also to this 

 formation. All along its lower limit, occur those peculiar associa- 

 tions of tuff and clay-shales described by Professor David and 

 Mr. Pittman from TamworthO), in which the tuff seems intrusive 

 into the chert. The origin of this structure is not clear. The 

 explanation of a somewhat similar feature at Lyndhurst, given 

 by Mr. Pittman(30), does not seem to apply here. In a large 

 measure, they may be due to crushing, for elsewhere brecciated 

 cherts are found, that seem to have been almost telescoped, and 

 the situation of the "tuff-intrusions," i.e., at the boundary of 

 tuff and chert, formations probably of very different powers of 

 mechanical resistance to pressure, would be very favourable to 

 such a crushing. But the same formation also occurs above the 

 radiolarian chert, in the Baldwin Series exposed in Cobbadah 

 Creek Gorge, where such crushing is out of the question. More- 

 over, the association seems to occur where tuffs lie on the clay- 

 stones or chert, and has not been noticed in the reverse case. 



It might be suggested, therefore, that were white-hot tuffaceous 

 material to fall on wet mud forming in a shallow or partially 

 dried lagoon, its heat might cause the mud to flake off and crack 

 away, and the commotion produced by the escape of steam, from 

 beneath, would give the stirring action necessary for mixing up the 

 flakes of mudstone and the tuffaceous material. In support of 

 this, it may be urged, that the flakes of mudstone are rarely more 

 than a few inches long, and are often bent like dried cakes of mud ; 



