256 GREAT SERPEXTINE-BELT OF NEW SOUTH WALES, vi., 



bottom, but, so far, no lake-deposits have been noted. To the 

 north of this is the Barraba township, on low undulating hills of 

 mudstone; and west of this, stretches the broad, matured valley 

 of the Manilla River. Here and there, on the higher hills, are 

 cappings of Tertiary river-drift, such as that on the hill by the 

 School House, and again on the hill behind the Barraba brick- 

 works, M'here fossil coniferous wood occurs among the gravels. 



The rock of the Barraba district is the type for the Barraba 

 mudstones, fine-grained, olive-green, flaggy rocks containing thin 

 layers of whitish felsitic tuff, and numerous casts of Lppidoden- 

 dron australe: and, in the finer portions, numerous radiolaria. 

 There are also a few bands of conglomerate, sometimes of a normal 

 character, more often with a strong tuffaceous base. 



About four miles west of Barraba, Hawkin's Creek joins the 

 Manilla. Here is a marked syncline; the westerly dip changes, 

 and, for some miles further west, an easterly dip predominates, 

 though at low angles. West, again, the river is crossed by 

 several bands of agglomerate (or repetitions of one band), between 

 which the river has been forced into its present extraordinarily 

 winding course. North and south of the river, these bands rise 

 into hills, with well-marked dip-slopes. South of Hawkin's 

 Creek, however, the bands of agglomerate do not appear, but 

 they are sharply cut off along the main road. This is probably 

 due to a fault, termed the Hawkin's Creek Fault, which may be 

 supposed to bring the mudstones to the surface on the southern 

 side of the fault. 



Practically nothing is known of the area for some miles south 

 of this point, save that it is chiefly composed of mudstones with 

 one or more resistant bands of tuffaceous conglomerate giving 

 rise to hills with gentle dip-slopes. 



West of the agglomerate-bands, the Manilla River traverses a 

 gorge cut through a great sill of dolerite-porphyry, which stands 

 out as a sheet fifty or more feet thick, forming nearly vertical 

 cliffs. This sheet has a gentle dip to the east, and, north and 

 south of the river, the sill can be traced by the well-marked 

 feature it makes along the line of hills. It is a continuation of 



