338 



GREAT SKRPENTIN^E BELT OV NEW SOUTH WALES, Vll., 



The chemical composition of the Loomberah limestone is seen 

 from the analyses below, which were made by the chemists of 

 the Geological Survey(13). 



1395 — Limestone, Portion 121, Nemingha (horizon not certain). 

 1220 — Limestone, Portion 58, Loomberah. 

 1784 — Limestone, Portion 23, Loomberah. 



Scrub Mountain Conglomerate. 



For about a mile west of the zone of the Loomberah limestone, 

 the sediments are a succession of cherts, radiolarian claystones 

 and tuff, the latter sometimes broadening out into coarse agglo- 

 merates, as in the case of the agglomerate to the west of the 

 upper portion of Cope's Creek. In Reedy Creek, however, the 

 rocks lose their cherty nature to a great extent, becoming mud- 

 stones almost indistinguishable from those of the Barraba Series. 



There is one very marked horizon in this portion of the section, 

 a zone of conglomerate which may be termed the Scrub Mountain 

 Conglomerate. It commences in Portion 17 and continues to 

 the south-east. It is made up of usually rounded or sub-angular 

 pebbles chieHy of a richly felspathic keratophyre, a strongly 

 trachytic type of which was found to contain phenocrysts of 

 felspar with abundant minute crystals of augite in the base(1474); 

 there is also some beautiful granophyre(1477, 1479), and, most 

 interesting of all, an angular fragment of radiolarian chert. 

 This last is not like the usual cherts of the Tarn worth Series, 

 being free from any sign of banding, but small amounts of a 

 rather similar rock do occur here and there in the Eastern Series. 



All these lie in a tuffaceous matrix. This has not yet been 

 studied microscopically, but from a macroscopic examination 



