GEOLOGY OF THE GLOUCESTER DISTRICT, N.S.W. 247 



(b) The Rhacopteris Beds. — These are quite thin; they 

 consist of tuffs with some shales, and immediately underlie 

 the Gloucester Buckets rhyolite flows. They contain the 

 following fossil plants : 



! Rhacopteris intermedia 

 (?) Aneimitcs (Rhacopteris) ovata 

 Cardiopteris polymorpha 

 Archceopteris sp. ind. 



Equisetales — Oalamitean stems. 



(c) The Gloucester Rhyolites. — These being a very strik- 

 ing development in this district, forming the back-bone of 

 the precipitous ranges which occur both to the east and 

 west of the town. They are particularly well seen in the 

 Gloucester Buckets (see fig.) where they are 1500 feet 

 thick, as also in the Mograni Mountain; good sections may 

 be seen in the railway cuttings immediately north of the 

 railway bridge on the Avon River. A number of flows are 

 included in the above thickness, but they are all very similar 

 in character. This lava is a typical rhyolite, light in colour 

 and frequently witli well-marked flow structure. It is 

 described in detail later on. 



A comparison of the Kuttung Series of the Gloucester 

 District with that of the Hunter River District some fifty 

 miles to the south reveals the following important differ- 

 ences (a) the relatively small thickness of this series in the 

 Gloucester District, as well as the almost entire absence 

 of the conglomerates whose great thickness is such a 

 characteristic feature of the Kuttung Series in the Hunter 

 River area, and (b) the apparently entire absence of glacial 

 beds in the Gloucester District. The broad details of the 

 Kuttung Series of the two areas are as follows : 



Hunter River District. Gloucester District. 



Ft. thick. Feet. 



Seaham Glacial Beds ... 1840 The Gloucester Rhyolites 1500 



Paterson Rhyolite ... 300 The Rhacopteris Beds 100 



Mount Johnson Beds ... 1950 The Conglomerates ... 150 



Martin's Creek Beds ... 2200 



Wallarobba Beds . 2000 



Total ... 8290 Total ... 1750 



