560 GRKAT SERPENTINE-BELT OF NKW SOUTH WALKS, v., 



from these limestones, the Upper Middle Devonian Series is a 

 monotonous succession of radiolarian claystones and cherts, with 

 lenticular intercalations of radiolarian limestone, frequent casts 

 of Lepidodendi'oti australe, preserved in the radiolarian rock, 

 with abundant masses of interstratitied and intrusive pyroclastic 

 rock, which show spheroidal weathering particularly well in the 

 railway-cuttings. The interstratified tuft's may also show casts 

 of Lepidodendron or contain radiolaria. 



The limestones which occur at the extreme south-eastern end 

 of the map, which, also, have been correlated with the Loomberah 

 limestone, and the cherts associated with them, probably belong 

 to this series; but the southernmost definite instance of its 

 occurrence is afforded by the rocks that form the western slopes 

 of West Gap Hill. The zone occupied by the series then follows 

 the flexions of the Lower Middle Devonian rocks, bending with 

 syncline and anticline, passes up Loder's Gully, and forms the 

 hills by the Tamworth trigonometrical station, and the western 

 slopes of the ridge extending to Moore Creek. Here the lime- 

 stone occurs in abundance, and is the type-occurrence of the 

 Moore Creek limestone. Only one band is present, but, as shown 

 on the map and sections, (Plates l.-li.) it is much folded, faulted, 

 and repeated. The previous writers have stated that the lime- 

 stone reaches a thickness of 1000 feet, but the writer has not 

 seen any section showing a thickness of limestone which one can 

 with safety assume to be more than 450 feet. The evidence 

 available is too poor to admit of a more definite statement than 

 this. The masses of limestone are lenticular in shape, and thin 

 out, and disappear about a mile south of the creek. They are 

 directly underlain and overlain by radiolarian cherts. 



The greater part of the Upper Middle Devonian Series is 

 repeated by the fault that runs along Spring Creek through the 

 Tamworth Common, which fault was discovered by Messrs. David 

 and PittmanO). This is not a simple fault, however, but a fault- 

 zone or plexus. In several places, the faults are made very 

 obvious by the fact that the adjacent rocks have been strongly 

 silicified or even metasomatically replaced by quartz, owing to 

 the action of siliceous solutions rising; in the fault-fissures. The 



