180 . GEOLOGY AND PETROGRAPHY OF CLARENCETOWN-PATERSON DISTRICT, i., 



State, and also in view of the fact that at the close of the Burindi epoch and 

 during the Kuttung epoch pronounced upwarping (not folding) affected the 

 area, it seems likely that the eruptions were of the fissure type. 



The question now presents itself as to how far the Mt. Gilmore Section may 

 be regai-ded as typical for, and indicative of the maximum thickness of the 

 Volcanic Stage. The overlapping of flows in a volcanic series must be looked 

 upon as a factor making for complexity and masking the truth concerning the 

 details of thickness, analogous to the factor of strike-faulting in achieving 

 similar effects. And while strike faulting often presents difSculty, the problem 

 of the stratigraphical variation caused by overlapping of flows may be more 

 subtle. In spite of this, one can be sure that there is a repetition, and therefore 

 an increased thickness from this cause, of no more than 300 feet in the Mt. 

 Gilmore Section. 



(iii.) Glacial Stage. 



The general sequence of the Glacial Stage is as follows: Basal conglomerates 

 overlain by red pebbly tuffs, the Glenoak varves, some thin bands of arkose, and 

 a thick mass of tuffs, grits, tuffaceous sandstones with conglomerate bands, and 

 local developments of volcanic breccia. Towards the top of the main mass of 

 tuffs (the equivalent of the Mt. Johnstone beds of the Paterson Valley) there 

 are fine-grained shales and tuffs carrying the remains of the Rhacopterk flora. 

 The Patei-son toscanite follows this thick clastic mass, and in its turn is suc- 

 ceeded by the Main Glacial Beds. The basal unit is a coarse conglomerate con- 

 sisting of pebbles up to two feet in diameter, granites, aplite and porphyries 

 occurring in abundance, with other types in less amount, all fairly well rounded, 

 but not showing evidence of long transportation. The best development of this 

 horizon is in Tumbledown Creek, just near Oakendale Homestead. This con- 

 glomerate is followed by tuffs with thin pebbly bands for about 200 feet, when 

 the Glenoak varves are reached. These are forty feet in thickness and present 

 all the features of the classic deposits at Seaham and elsewhere. The colour 

 varies greatly, the alternating bands of coaree and fine material sometimes being 

 red and white, as in the rocks west of the Seaham Hotel, and at other times 

 brown and yellow. Contemporaneous contortions are quite frequent, having 

 produced some beautiful structures. 



The varves are succeeded by the main tuffs which, on the whole, have a 

 very uniform gi'ain-size, and here and there contain bands of conglomerate. Mr. 

 Sussmilch has given a section of these rocks as seen on the eastern face of Mt. 

 Johnstone, where there is probably more conglomeratic material than anywhere 

 else in the area. In the valley of Tucker Ck., to the north of Hungry Trig. 

 Station, the tuffs grade into sandstones which suggest accumulation as continental 

 deposits. In some places the main tuffs are very fine-grained, this applying to 

 the strata which yield the Rhaoopteris fossils. Although the plant remains are 

 not restricted to one horizon, the strata in which they occur form a zone which 

 occupies in general a constant stratigraphic level, this zone extending from 50- 

 300 feet below the base of the Paterson toscanite. Arkoses occur in among the 

 main tuffs in rather restricted bands, as well as some interesting felspathic grits. 

 The latter have an abundance of orthoclase, possibly some plagioclase, both frag- 

 mental, and numerous chips of felsitic rocks all cemented by a ferruginous 

 matrix. These felspathic grits are exposed in a quarry on Reserve 112, Parish 

 of UfBngton, about a mile to the west of Glenoalc, the stratigi'aphical level being 

 about 500 feet above the top of the Volcanic Stage. About 100 feet above the 



