I!V W. \. BKXSON. 



69' 



Creek (1, b, pp.697-8; p.706, analysis); and a lainpmphyre, the 

 nature of which is not known to the writer, was found by Lieut. 

 Aurousseau in Portion 159, Attunga (see below). 



West of the Igneous Zone, there extends, through the Parishes 

 of Attunga and Burdekin, a monotonous series of banded cherts 

 and claystones with interbedded tuffs, giving, as a rule, very 

 unsatisfactory outcrops. These belong to the Upper Middle 

 Devonian Series, and contain masses of limestone. To the west, 

 the Upper Devonian rocks follow, forming the plains of the Peel 

 River. North of this, however, the central mass of Upper 

 Middle Devonian rocks seems to be flanked, to the east as well 

 as tt) the west, by Upper Devonian Mudstones; and, in Portions 

 47 and 48, Parish of Halloran, evidence of the occurrence of 

 an unfolded strip of Carboniferous rocks has been found by Mr. 

 S. M. Tout, lying adjacent to the serpentine, repeating, in this 

 manner, the features observed at Crow Mountain, and extending 

 ihence down to the Namoi River (1, d). 



The chief interest lies in the great masses of limestone, which 

 occurs here in greater abundance than in any other part of the 

 Great Serpentine Belt. Numerous separated masses lie within 

 the broad area marked as limestone in the map given in Part i. 

 (1, a). The resistance offered to erosion by the limestones is so 

 much greater than that of the claystones in which they occur, 

 that they generally rise into sharp hills, often thickly wooded 

 with pines. Just as in the region south of Moore Creek, these 

 masses of limestone prove to be isolated portions of folds, com- 

 pressed and faulted, the whole indicating an extremely complex 

 tectonic structure, though the intervening mass of claystone is 

 so imperfectly exposed, that no complete solution of the struc- 

 tural problem can be obtained. Thus, in the Parish of Attunga, 

 the mass in Portions 158 and 74 has the structure of a laterally 

 compressed dome or anticline, the axis of which pitches to the 

 north-west at the northern end of the hill, and south-west at the 

 southern end. It is faulted along the eastern side. The lime- 

 stone here is very thick, probably at least four hundred feet, the 

 lower two hundred feet or so being pure limestone, the remainder 

 with siliceous and other impurities. The hill behind the B. 

 50 



