BY W. N. BKNSON. 345 



a small complex, half a mile south of the south-eastern corner of 

 Portion 37, on the head of Bog Hole Gully, in which are ex- 

 hibited many of the features noted in the Hyde's Creek complex 

 (5, pp. 133-4). The keratophyre varies from a purely felspathic 

 type to a type irregularly blotched with areas enriched in mag- 

 netite, in a matrix of evenly coloured rock. There is also a 

 mass of more or less homogeneous magnetite-keratophyre, which 

 is, however, rather slaggy or vesicular, the openings being filled 

 with calcite (see p. 373). The margin of this irregular group of 

 intrusions is strongly jasperised, and the jaspers contain irregu- 

 larly distributed masses of haematite. There can be little doubt 

 that here also the ferruginous jasper has been developed by 

 solutions emanating from the keratophyre. 



Towards the southern end of the zone of keratophyre, where 

 it is sharply cut oflf by a fault, the rock becomes much brecciated, 

 and peculiar spherulitic masses are developed, which, when 

 microscopically examined, prove to result from intense secondary 

 silicification {see pp. 374-375). The rock is traversed by numer- 

 ous veins of quartz, and, in optical continuity with the grains in 

 these veins, there are roughly circular areas in which quartz has 

 entirely replaced the minutely granular groundmass of the rock, 

 and forms a matrix in which lie embedded the more or less 

 idiomorphic felspar-laths. Each of these areas weathers out like 

 a spherule. 



►Some long strips of highly silicified claystones are enveloped 

 in this mass. 



71ie ly neons Hocks of the Western Series. 

 1 . The Pyroclastic Ptocks. 

 The Igneous Zone. — One of the most continuous and strati- 

 graphically useful lithological horizons in the Tamworth Dis- 

 trict is the Igneous Zone, which there lies about 800-1,600 

 feet above the horizon of the Nemingha limestone. This 

 is not a definite horizon, but merely a lithological zone in 

 which pyroclastic rocks were constantly present, and were often 

 associated with intrusive rocks. This zone is not so clearly 

 marked in tlie Loomberah District, but seems to be here repre- 



