By W. N. BENSON, W. S. DON, AND W. E. BROWNE. 311 



There are, however, other peculiarities of the courses of streams which do not 

 appear to be referable to either of these causes [see Text-fig. 7) . The eastern 

 branch of Rocky Creek, for example, rises on the upper surface of the very resistant 

 Main Felspathic Grit, and owing to monoelinal shifting (in Gilbert's sense, 27), 

 the upper part of its course, which approximately follows the strike, has been 

 moved down to the western edge of the dip-slope of felspathic giit. The easterly 

 scarp of this dip-slope is very steep, but the stream, a mile from its source 

 turns back across the line of the highest ridges and for half a mile flows along a 

 niche cut in the scarp slope, before again turning at a sharp angle, and returning 

 through a deep gorge to the upper surface of the dip slope once more, down whicl; 

 it continues for the remainder of its course. Though no sign of fracturing has 

 been observed along the course of this lower gorge through the main grit, the ap- 

 proximate collinearity of a fault through the andesite in Sandy Gully, the gorge in 

 question, and the most important tributary to Anstey's Creek, may be not with- 

 out significance. 



We may compare with this the course of Upper Currabubula Creek, from 

 the western side of the main andesite sill through to the eastern, 

 where it is separated by a very low divide from the head-waters of 

 the tributaries of the Peel River, which it might be expected to join, 

 but instead of so doing, it returns through the gap in the andesite-sill and 

 flows north-westwards across the hard Kuttung rocks. Similarly, the western 

 branch of Rocky Creek continues approximately along the dip slope of a band 

 of (glacial?) conglomerate in the upper portion of the Kuttung Series, and is 

 very little entrenched therein, but just where it would be expected to foUow the 

 natural slope down into Anstey's Creek it turns at a right angle, forming a smaU 

 gorge through the conglomerate, to join the - eastern branch described above. 

 Again, there is the little gorge in which the western head-waters of Turi Creek 

 cut across the mass of pyroxenie andesite. Also, the passage of Werrie's Creek 

 through Kuttung rocks at the Gap to the west of the township, rather than south- 

 wards along the soft Werrie lavas in the depression followed by the railway line, is 

 apparently a striking instance of the want of adjustment of streams to structures. 

 These features suggest that the present drainage scheme is a super-imposed 

 drainage, now greatly modified by adjustment to structures through perhaps 

 several cycles of change, an idea for which tb.e writer is indebted to Mi'. W. R. 

 Browne. The presence of the Glossopteris sandstones at WeiTis Creek and in 

 several other districts to the south and north, and again of Permo-Carboniferous 

 marine rocks, and Glossopteris beds near Bowling Alley Point (25), both infault- 

 ed outliers, renders it probable that the intervening area was at one time covered 

 by Permo-Carboniferous or Permian strata lying perhaps unconformably upon 

 the Devonian and Carboniferous rocks. These have been almost completely re- 

 moved and the original valley system existing on these rocks has been superposed 

 upon the underlying complex of varied rocks. Tlie extent to which the present 

 drainage bears sign of its ancestry depends upon the ease of erosion of the rocks 

 upon which the drainage was superposed. Tn the Tamworth Plains, carved out 

 of yielding Barraba and Burindi mudstones, a high degi-ee of maturity has been 

 reached and a thickness of two tliousand feet of sediments may have been re- 

 moved from the greater part of the area. Where more or less resistant rocks oceui* 

 they have been brought into greater or less relief, notably at Round Mountain, 

 nine miles south of Tamworth, which is composed of a hard tufifaeeous conglom- 

 erate (26) and rises several hundred feet above the plain. It is also the case in 



