312 



GEOLOGV AXD PETROLOGY OF THE GREAT SERPENTINE BELT OF N.S.W. 



the Livei'pool Plains where the underlying stinietures seem to have been more 

 uniformly weak, and the base-levelling is more complete. But in the interven- 

 ing zone the valley systems superimposed on the diverse structures have retained 

 their position to a varying degree on the hard structures, though modified by 

 monoclinal shifting and the more rapid development of valleys on the softer stnic- 

 tures. 



This suggestion must be considered in connection with that of the eastern 

 margin of the Tamworth Plains, the discussion of which has been postponed 

 until this region should be studied. Keference should be made for this to the 

 topographic maps in the writer's previous papers (26) (28) (29) and to Text-fig. 

 9 herewith. The Moonbi Ranges to the north and south of Tamworth rise up 

 from the Tamworth Plains to a level of about three thousand five hundred feet, 

 rising to the south to four thousand feet, as about Hanging Rock. They are com- 

 posed of the resistant jaspers and cherts, the altered equivalents of the Lower 

 Tamworth (Middle Devonian) claystones and tuffs with perhaps older rocks 



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Text-fi^.8. Block tliau^i-am of the Tamworth District. 



grouped together as the Eastern Series. West of them there is the zone of un- 

 altered Tamworth rocks of less hardness, passing still westward into the Barraba 

 series of mudstones with resistant tuffs. This forms the zone of foothills of the 

 Moonbi Range, and in these differential erosion has had a considerable effect. In 

 the series of hQls in the Loumbcrah District, in which the ridges of harder rock 

 reach a level approximating to three thousand feet, we may see the greatly dis- 

 sected remnants of the plateau that once extended across to the Currabubula re- 

 gion, where again the resistant hills rise to a comparable general level. 



The course of the Peel River is of special interest. It rises in two main 

 head streams, Wombramurra Creek and the Peel River itself, which fiow for the 

 most part over the soft Barraba mudstones. the latter in a very open valley. 

 This closes north of Nundle as the harder cherts of the lower portion of the 

 Tamworth Series are encountered, and beyond the valley passes between steep 

 rough hills, through the jasperoid rocks of the eastern series from Bowling Alley 

 Point to Piallamore, but returns once more to the softer rocks of the Tamworth 

 Series, and thence on to the BaiTaba rocks of the Tamworth Plains. This alsD 

 may perhaps be an example, on a gi-and scale, of a superimposed river. 



But this does not exhaust the variety of physiographic interest of this region. 

 The small area lying between the Peel River and a line nmning north-north- 

 westward from Tamworth to Moore Creek (29) has many of the features of a 

 tilted block (see Text-fig. 8) . A very mature aggraded surface slopes from the 



