174 GEOLOGY AKD PETROGEAPHy OP CLARENCETOWN-PATEESON DISTRICT, i., 



lock, and foreign tuffaeeous material in a base of composition essentially similar 

 to the former, and the presence of secondary silica are thus explained. 



Succeeding- these peculiar rocks there is about 70 feet of a pale pink soda- 

 i-hyolite carrying some felsitic fragments. Albite is the chief constituent among 

 the phenocrysts, which are set in a pumiceous groundmass which has been im- 

 pregnated by secondary silica. Conglomerate succeeds the rhyolite and then 

 there follows a dark purplish rock, recalling the potash-rhyolite lower down in 

 the sequence. Phenocrysts of felspar dominate over fine-gTained quartz, both 

 being set in a dense base; the rock is a dacite. This is overlain by a band of 

 gritty-looking tuff, which possesses a characteristic appearance in thin section, 

 fragments of albite and quartz and patches of spherulitic material being cemented 

 together into a fairly compact mass. Following the tuff is a thick band of 

 conglomerate containing one well-defined band of medium-gTained tuff, which 

 consists of quartz and felspar chips and pieces of glassy and dacitic rocks. The 

 next horizon is a potash-rhyolite, in which a certain amount of brecciation dur- 

 mg consolidation has occurred. This is not well-developed, fresh outcrops being 

 rare, and it is succeeded by a tuffaceous felsite, which has resulted from the 

 ■showering of quartz, felspar and pitchstone fragments into a flow which solidified 

 BS a pumiceous groundmass to these fragments. This rock ends under the last 

 unit in the Volcanic Stage, which is a fine-grained rock with quartz, felspar and 

 biotite showing in hand-specimen, its microscopic characters not yet having been 

 investigated. 



Summarising the Langlands Section we have : 



Thickness in Feet 



Hypersthene-andesite-glass 50 



Conglomerate and tuffs . ■ 550 



Rhyolite ' 36 



Conglomerate 90 



Quartz-keratophyre . 55 



Potash-rhyolite 18 



Dellenite-toscanite 40 



Tuffaceous volcanic conglomerates and flow-breccias 35 



Soda-rhyohte 70 



Conglomerate ■ IS 



Dacite . . . . lOS 



Gritty tuff 70 



Conglomerate with well-defined tuff band 292 



Potash-rhyolite 50 



Tuffaceous felsite 20 



Fine-grained lava (Possibly a keratophyre? ) 18 



Total Thickness 1520 



The Glenoak Section. (E-F on Map). Text-fig. 2. 



The Volcanic Stage rocks developed along the line E-F from Glenoak to 

 the south, present many interesting features. 



We commence immediately to the north of the Post-Office upon the base 

 of the hypersthene-andesite-glass, which is fairly well-developed here, the dip 

 being flat to the south. Overlying it are red tuffs with pebbles here and there. 

 They are followed by a decomposed biotite-quartz-keratophyre, the outcrop of 

 which has a considerable extent on account of the low angle of dip mentioned 

 above. In the weathered state the biotite shows up very well. To the west 

 of the line of traverse the rock is found in a fresh state. Above it comes the 

 peculiar volcanic conglomerate described in the Langlands Section. Here there 

 are abrupt changes from the type of rock containing many rounded inclusions 



