386 W. R BROWNE AND A. B. WALKOM. 



mostly on and around the Post Office Hill, and liave under- 

 gone very violent and extensive contortion, apparently 

 when in a plastic condition and also subsequent to consoli- 

 dation. The rhyolite is as a rule strongly banded, and the 

 even course of the banding is often broken by folds varying 

 from a fraction of an inch to several feet across. Persistent 

 tilting of the rock mass is observed, the flows dipping at 

 various angles in an average direction of about N. 10° E. 

 The beds are cut off abruptly by the small submeridional 

 fault already referred to, which also at its southern end 

 throws down the trachyte against the rhyolite. 



The rhyolite is mainly of the glassy type, no porphyritic 

 quartz crystals being seen as is the case with the Mount 

 Bright rock. What appears to be secondary material of a 

 jasperoid nature, dark brown to black in colour, is of fre- 

 quent occurrence. There is evidence of several successive 

 flows in this area, the earlier of which were brecciated by 

 the later eruptions. Fine rhyolite tuff also occurs in con- 

 siderable abundance, and a hard green tuff which is spar- 

 ingly found seems to be a modification of the rhyolite tuffs. 

 Trachyte overlies and partly surrounds the rhyolite. It is 

 in places of a tuffaceous nature, and is of the leucocratic 

 or acid type, light brown in colour. The andesite probably 

 represents the remnants of former flows on top of the 

 trachyte or intrusive into it. 



An outcrop of chocolate shales and dark coloured con- 

 glomerate is exposed in the bed of a creek on the Rothbury 

 Road, not far from the Post Office. These are entirely 

 different in appearance and constitution from the known 

 Permo-Carboniferous rocks, for which reason they have 

 been put down as Carboniferous and correlated with similar 

 occurrences in the other areas. 



Monnt Bright Area, — Here a very much older formation 

 is met with in the shape of grano-diorite; as its age may 



