182 GEOLOGY AND PETROGRAPHY OP CLAREXCETOWN-PATERSON DISTRICT^ i., 



one would expect to find the sill in a dift'erent stratigTaphical position from the 

 extruded portion, but the fact remains that the Paterson rock is found at a 

 constant level all through the area. 



Thus the matter must be left an open question for the present. From 

 general impressions and experience in the field, the writer is inclined to view 

 the whole of the rocks as extrusive, feeling that the discrepancies described 

 above will eventually be explained; but no definite pronouncement will be given 

 in the present state of knowledge. 



iWhatever the mode of occurrence of the rocks under discussion, there is a 

 definite variation in the chemical composition from place to place. To the 

 west of Paterson there are two varieties, the lower one being a buff-coloured 

 rock of the nature of a spherulitic toscanite, and overlain by a type transitional 

 between potash-rhyolite and dellenite, this being purple in colour, and showing 

 an abundance of free quartz. At Paterson Station where the mass has decreased 

 in thickness to about 90 feet, there is only one definite variety, in which the 

 quartz is not so abundant megascopically, but is probably in the gToundmass. 

 Under the microscope the plagioclase is seen to be andesine of basicity less than 

 that in the rock on Mt. Johnstone, while biotite and ortlioclase are present in 

 fair amount, the rock being either a dellenite or a toscanite. The maximum 

 development of these rocks occurs at Himgry Hill, where they attain a thickness 

 of 290 feet. Here the mass is of a threefold nature. The first 200 feet is com- 

 posed of a handsome toscanite with a general brown body-colour, and well-formed 

 phenoerysts of quartz, orthoclase and plagioclase. Above it lies a small band, 

 probably 30ft. thick, of a felspathie phase, the rock being intermediate between 

 toscanite and andesine-dacite. The third variety is a pale-blue toscanite, some- 

 what sirdilar to the first type. Between Hungry Hill and the east side of the 

 Williams River, 'these rocks vary considerably in lithological features, and the 

 thickness never exceeds 100 feet. Examination has been made of slides of the 

 reek in I'elspar Creek, just west of the main road, which is a dellenite, and 

 of the rock a little to the east of this, which has a distinctive greyish-gTeen 

 colour and proves to be less acid and almost a dacite. 



Opposite Porphyry Point, on the left bank of the Williams, the Paterson 

 type of rock occurs as a mass 150 feet thick. From a careful examination of 

 fresh hand-specimens there appear to be three phases present. The first is 

 grey rock with few phenoerysts of quartz and felspar, followed by a fluidal 

 purple rock with abundant phenoerysts, which passes into a blue rock which 

 weathers to a buff colour. No microscopic examination of these rocks has been 

 made, but W. R. Browne states (Sussmilch and David, 1919, p. 289) that del- 

 lenite and rhyolite occur hereabouts. 



The only important area, other than Paterson and Seaham, where the Main 

 Glacial Beds are well-exposed, is the Dunn's Creek district. Here they are 

 developed in an asymmetric pitching syncline. A generalised section obtained 

 from data collected in Dunn's Ck. and its tributaries is as follows : 



On the eastern side of the syncline the basal rocks are tuffs, containing 

 bands of nondescript material, clearly of glacial origin. Here and there groups 

 of pebbles occur, and in one of these a faintly-striated boulder was found. These 

 tuffs which have a thickness of 350 feet are found again at .Seaham. On the 

 western side of the syncline, the basal unit is a thick mass of flu\do-giacial 

 conglomerate and tillite. These rocks are exposed all along the course of Dunn's 

 Ck. from portion 50 to portion 14, Parish of Butterwick. In places they are 

 almost true tillites, but on the whole consist of badly-sorted rounded and sub- 

 rounded boulders of variable size, including repi'esentatives from the underlying 



