354 GREAT SERPENTINE BELT OF NEW SOUTH WALES, Vli., 



but was shortly interrupted by the outbreak of the volcanic 

 action which formed the Silver Gully Agglomerate extending 

 from Black Jack to Hyde's Creek, the centre of eruption 

 being probably near the southern margin of the map herewith 

 (Plate xxxii.). 



Further radiolarian sedimentation followed, with minor 

 volcanic outbreaks, until the more extensive eruptions occurred 

 which liave produced the pyroclastic rocks of the Igneous Zone, 

 which are not as thick in the region under discussion as they 

 are in the districts to the north and to the south. Associated, 

 apparently, with this eruption was the intrusion of several 

 dolerite-sills lying below the horizon of the pyroclastic rocks of 

 the Igneous Zone. The sills exposed within the Loomberah 

 Parish are of normal composition, that to the south of Loomberah 

 being albitic. Whether the keratophyres below the Nemingha 

 Limestone were injected at this period or not, cannot be deter- 

 mined at present; they were evidently formed under a consider- 

 able cover of sediment. All the tuffs contain fragments of coarse- 

 and fine-grained keratophyric material (but not fragments of 

 ferruginous jasper). 



Radiolarian sedimentation ensued once more, and the deposi- 

 tion of the Loomberah Limestone followed, the limestone rising 

 in places above the surface of the sea, so that it has distinctly 

 the features of a littoral formation. Nevertheless, the radio- 

 larian mudstones above and below it are quite of the normal 

 tvpe, the former containing abundant small intrusions of acid 

 tuff 



Following the deposition of the Loomberah Limestone is a 

 series of radiolarian claystones and tuff. The most important 

 centre of eruption was near the head of Cope's Creek, the bands 

 dving away rapidly to the north, but continuing some distance 

 to the south. A less important centre of eruption lay near the 

 north-western end of the area mapped, in Calala Parish. Above 

 these agglomerates, the radiolarian clayslone gives place to a 

 radiolarian mudstone, softer, and not quite so finely granular as the 

 former rock. No sign of the Moore Creek Limestone is present, 

 though it might be expected near this region of change in char- 



