BY W. X. BENSON. 227 



and sections were given in the first part of this series in 1913(1). 

 These are reproduced in the present article. Constant reference 

 will be made to this first paper, and to the third part of the 

 series, which deals with the petrology of the rocks collected. 



Stratigraphy and Tectonics. 



The stratigraphical succession in this region has been described 

 in previous papers (1). Biiefly, it consists of (i.) the Devonian 

 System, comprising (a) some possibly Lower Devonian phvUites 

 and jaspers in the general complex known as the Eastern Series, 

 i.e., the rocks lying east of tlie Serpentine Line; (b) the Middle 

 Devonian, Tamworth Series of radiolarian cherts, claystones, 

 tuffs, breccias, and limestones occurring on the Namoi River and 

 to the south and ^^ est of Bingara, and forming a great part of 

 the Eastern Series; (c) the Baldwin Agglomerates (the lower 

 portion of the Upper Devonian Series), which form the central 

 portion of the region mapped, and extend for eighty miles north 

 and south, and fifteen miles east and west; and (d) the Upper 

 Devonian, Barraba mudstones with interbedded tuffs, conglomer- 

 ates, and, rarely, doleritic sills. The last three formations are 

 conformable one with the other, and are conformably overlain 

 by (ii.) the Lower Carboniferous System, consisting of (e) a 

 lower series of marine mudstones and limestones, the Burindi 

 mudstones; followed by (/) the Rocky Creek Conglomerates 

 with interbedded felsitic tuffs and some felsites. The whole 

 series has been folded by forces thrusting from the east, which 

 have produced close packed folds and much faulting in the 

 eastern portion of the region, with the formation of one pre- 

 eminent and continuous line of fault, into which has been 

 injected an almost continuous mass of ultrabasic rock. West of 

 this "Serpentine Line," the folding decreases in intensity, pass- 

 ing from isoclinal folds dipping steeply to the east, to mere 

 undulations, more or less broken by faults. This folding took 

 place before Permo-Carboniferous times, and may have been con- 

 tinued at intervals till near the close of tlie Permo-Carboniferous 

 period, but died out before the deposition of the Upper Pernio- 



