BY G. D. OSBORNE. 185 



It is interesting- to note that the stratigraphical interval between the lava 

 and the marine elaystones is occupied by rocks which are not homogeneous for 

 any distance along their strike. The persistence of the two horizons precludes 

 the possibility of dip-faults, and here the lenticular and local nature of some 

 of the beds in the Burindi Series is again well exemplified. 



The Burindi rocks to the east of Mt. Gilmore owe their position to heavy 

 strike faulting (see Plate xsvi.). They outcrop over an area of about two 

 square miles in the region mapped, their extent to the north being unknown. 

 The plan of the outcrop is triangular, with the apex in portion 55, Parish of 

 Wilmot. One can not make out very clearly the distribution of the individual 

 horizons in this area, but there is undoubted eyidence of only local development 

 of the various types. Thus the pitchstone outcropping in portion 56, Parish of 

 Wilmot, can be followed for about three chains, and then is not encountered 

 until one comes to the northern end of portion 59. This flow is interbedded 

 with tuffs and conglomerate bands which pass into elaystones as one travels 

 north into portion 52, Parish of Wilmot, and the outcrop of these elaystones, 

 which are locally silieifled, is continued for about ten chains, when coarse gritty 

 tuffs and tuffaceous sandstones obtain. These in turn decrease in extent going 

 northwards and then one finds acid tuffs which outcrop on the Limeburner's 

 Road, just east of the five-mile peg. These latter are clearly of primary de- 

 position, and in places of the nature of "flow-breccias," but the former have to 

 some extent been redistributed, and are mixed with a certain amount of arenace- 

 ous sedimentary material. It is possible that some of the abrupt changes along 

 the strike which characterise many of the Burindi elastic units may be due to 

 partial contemporaneous erosion of one series and subsequent accumulation of 

 another series. 



The Kuttung Series. 



(i.) Basal Stage. 



The basal conglomerates of the Kuttung Series form part of the Wallarobba 

 Eidge (incorrectly called a range), and are exposed on the northern fall of that 

 ridge, and artificially in the cuttings of the Railway. On account of the plung- 

 ing syncline at AVallarobba, which is clearly indicated by the outcrop of the 

 homblende-andesite of the Volcanic Stage, the conglomerates swing off to the 

 North-east, and are seen on the road to Sandy Creek. The chief "tuff-portion" 

 of the Basal Stage forms the rocks in the southern end of portion 1, Parish of 

 Wallarobba, and then is lost in the alluvium of Sandy Creek. 



The next place of distinct occurrence of Basal Stage rocks is to the oast- 

 south-east of Wallaroo Hill, forming an eminence in State Forest No. 178 (Uf- 

 fington) ; the strike of the sediments here is more or less east and west, so that 

 the conglomerates are exposed on .the Maitland Road about three and a half 

 miles from Clarencetown. With a changing strike the rocks then curve round 

 till they assume a north and south trend and appear in the paddocks lying to 

 the west of the Williams River. Ultimately they cross through the western out- 

 skirts of the town, showing up well on the Dungog Road and near Clarencetown 

 Bridge, while a small area to the east of the river is also occupied by the out- 

 crop of these rocks. 



The failure of the conglomerates and tuffs to appear between the eminence 

 in State Forest 178, and Wallarobba may be due to faulting, but it seems more 

 likely that these rocks occur as large lenticular masses, not forming a continuous 

 unit between the localities cited. 



