'2t'J GREAT SERPENTINE-BELT OF NEW SOUTH WALES, VI., 



West of this, the mudstones are overlain by the Rocky Creek 

 conglomerates; and at the head of Bobbiwaa Creek, Dr. Jensen 

 found coal-bearing Permo-Carboniferous sandstones and shales 

 (31). To the south, on Boomi Creek, he noted that the valley is 

 cut in conglomerates, with rhyolitic and andesitic tuffs and 

 quartz-porphyries, which are the same as those seen in Maule's 

 Creek to the south. All these, he classed as Permo-Carbonifer- 

 ous, following the State Geological Map of 1 893. It seems most 

 likely, however, that these are the Lower Carboniferous con- 

 glomerates of the Rocky Creek Series, and the writer's map 

 (Plate xix.) differs from the earlier one in this respect. 'J'he 

 new boundaries were plotted after discussion with Dr. Jensen, 

 who has generously requested that it be added that he concurs 

 in the changes made. In the south of this region, Dr. Jensen 

 has noted the unconformity between the Coal-Measure sand- 

 stones and the Carboniferous conglomerates. The boundaries 

 of the basalts east of the Nandewar Mountains are based partly 

 on Dr. Jensen's maps, and partly on unpublished observations 

 by Mr. L. F. Harper, F.G.S., of the State Geological Survey. 

 The details of the other volcanic rocks of the Nandewar 

 Mountains have been fully discussed by Dr. Jensen in the work 

 cited (31). 



Physiography. 



The most accurate account of the topography of this region 

 seems to be that given by Mr. Andrews in his first discussion of 

 the physiography of New England (32). While the effects of 

 uplift are noted, due importance is attached to differential 

 erosion in hard and soft structures. To this, rather than to 

 differential movement, warping or faulting, the local relief ap- 

 pears to be due. Nevertheless, the effects of differential uplift 

 have determined the broad features of the distribution of elevated 

 regions and plain. These will be considered first. 



i. Features due to Differential Movement. — The plateaux of 

 New England sink to the west, and pass out into the plains 

 between Bingara and Warialda. Between Manilla and Tarn- 

 worth, a rapidly rising series of rugged foothills carries the land- 

 surface from the low plains of the Namoi and Peel Rivers to the 



