BY W. N. BENSON. 695 



The region exhibits a varied series of formations. From 

 Willowtree Creek northwards, there extends intermittently the 

 line of serpentine-intrusions. To the east of this are the crushed 

 and altered rocks of the "Eastern Series," which here belong, 

 apparently, to the Lower Middle Devonian formation, in great 

 measure. They consist of crushed and sheared, banded cherts, 

 agglomerates, and volcanic breccias, with lenticular masses of 

 limestone, probably of the Nemingha horizon; and, here and 

 there, a mass of serpentine. This can be well seen along the 

 Valley of Wiseman's Arm Creek. Between these and the Ser- 

 pentine, however, is a long ridge of red jasper culminating in 

 the peak Bungemullagalarno, south of Hall's Creek. North of 

 this creek is a low gap leading to the Namoi River between the 

 jasper ridge by the Serpentine line to the west, and the scarp of 

 the New England plateau to the east, a scarp which is, in part, 

 of tectonic origin. 



The serpentine varies greatly in width. It is scarcely more 

 than a yard wide near Willowtree Creek, but is nearly a quarter 

 of a mile wide by Hall's Creek. The larger masses of serpentine 

 here do not occur in the Serpentine Line, but strike north from 

 near Ukolan through the above-mentioned gap to Mundowey, 

 thus indicating a virgation of the tectonic lines. 



Returning to the south : near the head of Horsearm Creek, 

 limestone occurs, and extends across into Willowtree Creek, 

 where the outcrop reaches a width of nearly 400 yards, probably 

 broken by faults. It dies out before reaching Attunga Creek, 

 but appears again north of the creek (in Portion 151, Burdekin), 

 where it is very tuffaceous, weathering to a cavernous rock. 

 This suggests that this limestone belongs to the Nemingiia 

 horizon, which is supported by the abundance of igneous material, 

 tuffs, breccias, dolerite, etc., immediately west and stratigraphi- 

 cally above the limestone, which probably indicates the position 

 of the Igneous Zone known to overlie the Nemingha limestone 

 (l, c). Beyond Portion 151, the Nemingha limestone passes to 

 the east of the Serpentine Line, and its extension has been traced 

 up through Wiseman's Arm Creek to Crow Mountain. It does 



