176 GEOLOGY AND PETROGRAPHY OP CLARENCETOWN-PATERSON DISTRICT, i., 



Rocks of the Volcanic Stage are well exposed in a series of dip-slopes 

 running down to Tumbledown Creek. The section starts upon a thick mass of 

 conglomerate overlying the biotite-quartz-keratophyres which all through the 

 area are the first important flows to succeed the hypersthene-andesite. The 

 rocks following the thick conglomerate are as follows: 



Text-fig. 4. The Oalcendale Section. (Line G-H on map 



diameter 



of ridges 

 of quartz 



(a) Acid tuffs. These rocks vary a little in texture from point to point, 

 but in general have an average uniform grainsize, and a general nisty-red 

 colour. The constituents are angailar quartz in abundance, biotite-pitchstone, 

 pumice and felsite fragments, all cemented together by a matrix, which has now 

 been completely stained by iron. Thickness, 50 feet. 



(b) Conglomerate. Pebbles of great variety up to nine inches : 

 set in a reddish gi-itty matrix. Thickness, 80 feet. 



(c) Dacite. This rock forms a pronounced bump on the line 

 traversed by the section. It is fairly fresh and shows an abundance 

 in hand-specimen. The microscope reveals large corroded quartz crystals and 

 some ragged oligoclase-andesine in a partially glassy base. Thickness, 70 feet. 



{d) Conglomerate. This is similar to the preceding conglomerate (6), 

 but the size of the constituent pebbles is somewhat less. Thickness, 50 feet. 



(e) Dellenite. This is the most important massive rock, outcropping from 

 the line of section down to Tumbledown Creek, and along the right bank, west 

 of the section. It is very well exposed artificially on a road nearby, fresh speci- 

 mens having a fawn colour, and displaying the existence of porphyritie quartz, 

 orthoclase and acid plagioelase in an extremely fine-grained groundmass. Thick- 

 ness, 40 feet. 



(/) Tuff. This is not very thick, being very weathered and possessing a 

 yellow colour and a gTitty nature. Thickness, 35 feet. 



(g) Fine-grained cherty rock. These rocks, although only 20 feet thick, 

 deserve careful notice. They show many lithological features identical with the 

 varves of the Glacial Beds. The hard porcellanous appearance of many of the 

 latter is a characteristic of the rocks here, and irregular alternation of fine and 

 coarse layers is to be noted. Nevertheless, there is no evidence of contem- 

 poraneous contortion, nor of associated glacial rocks, so tliat one cannot assign 

 to them a definite origin. Thickness, 20 feet. 



