BV \V. X. BENSON. 



141 



are regular diorite-arkoses (see, for instance, the description of 

 M.B. 6-3, 1, Pt. iii., p.719), while others are more andesitic. 

 Associated with these are hard, cherty layers. This continues 

 right up to the serpentine, and may be traced northwards as far 

 as the head of Oakey Creek, making a well-marked range of hills 

 all the way. This formation has been doubtfully mapped as 

 belonging to the Burindi Series. Another possible alternative 

 is that adopted in 8ecti(jn l^, Plate xx., where the rocks have 

 been classed as of Barraba age in view of the great similarity 

 between some of the tuffs present, to some that occur in the 

 upper part of the Barraba Series below the basalts at the head 

 of Sheep Station Creek, near Cobbadali. The evidence as yet is 

 entirely insufficient to come to any conclusion. 



Farther down Cobbadah Creek are mudstones of the same 

 character as those of the Burindi Series, bent into a series of 

 sharp anticlines thrust over to the west, and broken by a fault 

 along each anticlinal crest, in the manner usually figured in 

 diagrams of isoclinal folding. Beyond, near Piedmont homestead, 

 three miles east of Cobbadah, the creek is crosssd by a bar of 

 the peculiar olive-green shale, with little blebs and narrow bands 

 of impure limestone, that is so characteristic of the Burindi 

 Series. West of this is a well-marked fault, which separates the 

 Burindi rocks from the Barraba Series lying to the west. A 

 little to the south-east of the Piedmont homestead, in a tributary 

 of Cobbadah Creek, and in or near the line of this bounding 

 fault, is a small bar of pink carbonate-rock with a talcose matrix 

 and a little hcematite, probably the "gossan" of a small intrusion 

 of serpentine. This is one of the very few instances of the 

 occurrence of serpentine ivest of the main Serpentine Line. 



About nine miles north of this region, the Burindi rocks have 

 been studied immediately west of the Serpentine Line at the 

 head of Hall's Creek (see eastern end of Section No.S, Plate xx.). 

 Just at the corner of the road at the bottom of the Devil's 

 Elbow, which lies on Barraba rocks, is a little tributary of 

 Hall's Creek, beyond which rises a narrow band of unmistakable 

 talcose, carbonated serpentine, traceable a hundred yards to the 



