132 GREAT SERPENTINE BELT OF NEW SOUTH WALES, iv., 



The doleritic type is abundant, but does not exhibit pillow- 

 structure. It has not been possible to determine the mode of 

 occurrence of these rocks. They lie in the most disturbed zone 

 in the Bowling Alley rocks, and the steep scree-covered slopes on 

 either side do not expose any lines of contact between the sedi- 

 ments and the igneous rocks. It is almost certain that the series 

 is faulted and folded, probably in a syncline. The occurrence of 

 the breccia on both sides of the creek may be due to this; lines 

 of shearing are to be seen in the rock. It is not clear, also, 

 whether any of the rocks were actual flows. At the southern 

 extremity of the mass there is a band of variolite only a yard 

 thick, lying in a rather wider band of decomposed flow-breccia. 

 The line of contact between this and the sediments is indecisive. 

 There is also no clear evidence as to the relation between the 

 variolitic leucocratic rocks and the strongly magnetitic spilite, 

 described above as intrusive into a limestone. There seems to 

 be almost a passage between the two types. In the creek below, 

 pillowy spilitic boulders are associated with the variolites, and 

 here again passage-rocks seem to occur, but the relation of the 

 two types in situ is unfortunately obscured. A passage from a 

 rock free from magnetite into one rich in that mineral is not 

 impossible, as will appear from the consideration of the magnetite- 

 keratophyres. A dyke of odinite traverses the series. 



The most remarkable of all the rocks are the keratophyres. 

 Of these are to be distinguished the keratophyres proper, the 

 magnetite-keratophyres, the quartz-magnetite-keratophyres, and 

 the quartz-keratophyres. The simplest occurrence is that of the 

 keratophyre at Hanging Rock, which has been mentioned pre- 

 viously (Part ii., p.586; Part iii., p.666). It is also in a zone of 

 great disturbance, and its relations are obscured. It seems pre- 

 ferable to consider it as a short sill, rather than as a volcanic 

 plug. The rock is made up almost entirely of plagioclase, and 

 analysis shows its extremely sodic character. 



The magnetite-keratophyres are linked by passage-rocks both 

 to the spilites and to the keratophyres. In the one sequence, 

 the spilite passes into magnetite-keratophyre by the gradual 

 diminution in the amount of augite present, and the increase in 



