250 



THE GEOLOGY AND PETROLOGY OF THE GREAT 

 SERPENTINE BELT OF NEW 80UTH WALES. 



Part vi. A General Account of the Geology and Physio- 

 ORAPHY of the Western Slopes OF New Enoland. 



By W. N. Benson, D.Sc, B.A., F.G.S., Professor of Geology, 

 University of Otago, N.Z.; formerly Linnean Macleay 

 Fellow of the Society in Geology. 



(Continued from p. 2 45.) 



iv. The Middle Wester7i Zone. 



Ill this zone, we will consider the belt of country between the 

 zone last described and a line running west of Black Mountain, 

 Blue Knob, and the Bingara Range. It consists of Barraba 

 Mudstones and Baldwin Agglomerates, with some Tertiary Drift 

 and Basalt. The Agglomerate forms most of the high land of 

 the region except Blue Knob, a great dolerite-sill. Structurally, 

 the region consists of beds dipping gently to the east, for the 

 most part merging gradually into the steep, easterly-dipping, 

 isoclinal folds to the east, or sharply divided therefrom by a 

 fault. On the western side, the sediments dip gently to the 

 west for the most part. The whole series is broken by a group 

 of faults, running between N. and N.N.E., and sometimes 

 branching, throwing the beds down to the west, as a rule, in the 

 southern portion of the zone, but also to the east in the 

 northern portion. 



Commencing in the south — The Lower Manilla River runs in 

 a syncline of Barraba Mudstones (see Plate xx., fig.l). To the 

 east, the Baldwin Agglomerate rises to form Pyramid Hill, which 

 is cut off by a fault to the east, beyond which lies the more 

 steeply dipping Middle Devonian Series. Traced to the north, 

 the agglomerates disappear, and also the Middle Devonian beds 

 wedge out, and the Barraba Mudstones extend, with ever increas- 



