556 GREAT SERPENTINK-BELT OF NEW SOUTH WALES, v., 



rock is the same as that of tlie more finely granular spilite-por- 

 phyrites, and contains some well shaped phenocrysts, bui the 

 majority of the larger grains, which are only 0-2 mm. in diameter, 

 are fragments of albite-crystals. There are also fi-agments of a 

 pilotaxitic, f el spathic rock rather poor in ferromagnesian minerals 

 (keratophyre), as well as others richer in these minerals (sf)ilite). 

 This rock is one of the most finely granular of the rocks which 

 seem to have a character intermediate between that of massive 

 and pyroclastic types. 



The petrological character of this complex must be our guide 

 to further uiu-avelling the stratigraphy of the Lower Middle 

 Devonian Series. The wide alluviated valley of the Cockburn 

 River obscures any direct linking of the formations across the 

 stream, but the exact equivalent of the Tintinhull spilite is 

 found to form the small hill in portion 48, Parish of Nemingha, 

 by Pullman's farm. The hill, which is probably divided by a 

 fault, consists of two masses of porphyritic spilite, separated by 

 a band of pyroclastic material. The upper mass shows some 

 indefinite signs of ellipsoidal partings. The dip of the associated 

 beds (W. 10° N. at 40°) shows that a syncline exists below the 

 river, and that this spilite-mass may well be the same band as 

 that occurring at Tintinhull. As this rock was fairly free from 

 epidote, it was chosen for analysis, and proves to be thoroughly 

 albitic(see No.ll30, p.602). 



Eastward of this hill, are phyllitic claystones and quartzitie 

 rocks, resembling those that lie between the Igneous Zone and 

 the limestone. But, in place of the limestone, the igneous band 

 appears again, southwards from portions 66/148; its reappear- 

 ance is probably due to a fault, rather than to anticlinal folding, 

 as the dip is to the west also. Tlje igneous series here consists 

 chiefiy of pyroclastic material, but on its eastern side is a mass 

 of porphyritic spilite like that at Tintinhull. The thick pyro- 

 clastic series extends southwards for over two miles, and forms 

 the greater part of the hill, which we will term West Gap Hill 

 (see Topographical Map, PI. xlix.j. The indented outline of the 

 igneous rock, and its repetition, probably indicate the presence 

 of a group of strike-faults here. The nature of the rock varies 



