188 GEOLOGY AND PETROGRAPHY OF CLARENCETOWN-PATEESON DISTRICT, i., 



of portion 160, Parish of Uffington, where the andesite, now very thin, appears, 

 one can follow tlie outcrop with ease across to the Williams Eiver and the foot 

 of the Mt. Gilmore Ridge, the rock failing temporarily at the cross-road to 

 Seaham (see map). 



The distribution of the hypersthene-andesite and andesite-glass is in general 

 agt'eement with that of the Martin's Creek type, but the former is not so wide- 

 spread. It is found in the paddocks west of the railway near Martin's Creek 

 Station and in the i-ailway cutting a little to the north of the Station, where it 

 has been brought up against the hornblende-andesite by a small overthrust fault. 

 While its thickness hereabouts is 100-150 feet, a short distance to the east it is 

 hard to discover, and in portions 16 and 29, Parish of Barford, it has a limited 

 extent, being about 15 feet thick. Near the upper part of Tumbledown Creek, 

 two outcrops are seen, viz., in portions 22 and 57, and 34 and 59 respectively. 

 These appear to be the result of a small branch fault. The hypersthene-andesite 

 is not seen again until one comes to the village of Glenoak, where about 200 

 acres are occupied by its outcrop. This occurrence is bounded on both the west 

 and east by faults, the eastern fault being responsible for displacing the andesite 

 some distance to the north, its outcrop being seen on the main road about li 

 miles from Glenoak. From here, intermittent exposures occur towards the Wil- 

 liams Eiver, but east thereof the rock is only found at the foot of the northern 

 end of Mt. Gilmore, in portion 16, Parish of Wilmot. 



The biotite-quartz-keratophyre (Williams River type), of which there are 

 in most places two flows separated by a little conglomerate, has its maximum 

 development in the eastern part of the area. In portion 10, Parish of Wilmot, 

 on the Williams River it is exposed in a large quarry, and must hei-e be about 

 150 feet thick in the larger flow and 30 feet in the subsidiary one. With the 

 exception of the districts of Martin's Creek, the Langlands Estate and the 

 northern end of Mt. Gilmore, one finds over all the area the two flows which 

 microscopic examination shows to be almost identical. 



Passing west from the Williams River quarry, the keratophyre abruptly de- 

 creases in extent and is poorly developed between the river and Glenoak. At 

 the latter place it is decomposed and, on account of its flat dip, occupies a 

 comparatively large area just south of the Post Ofiice. Heavy faulting then 

 intervenes, and it is next found in the fields to the north-east of Oakendale home- 

 stead. The exact relationships of the outcrops here to the surrounding rocks 

 are not clear. However, to the north-west of "Oakendale," one finds the two 

 flows with their usual stratigTaphical relationships, as on the cleared hills north 

 of Tumbledown Creek. The large fault which runs through this locality, pass- 

 ing the hornblende-andesite ridge of portion 99, Parish of Barford, terminates 

 the keratophyres on the west, and they are not found till one comes to a tribu- 

 tary creek in portion 137, from whence the main flow (the subsidiary one having 

 died out) can be traced westwards past the Martin's Creek school to the railway 

 line, where it is adjacent to the hornblende-andesite. To the west of the railway 

 the rock is found in Priestley's paddock (S.E. division of portion 131, Parish of 

 Barford), the outcrops being for the most part decomposed. 



Some idea of the distribution of the remaining lavas of the Volcanic Stage 

 has been given in the discussion on the stratigi'aphical variation, but something 

 must be said of the important unit which has been termed the Mt. Gilmore 

 biotite-dellenite. This rock displays very well the manner in which some of the 

 lavas change their facies from place to place. At the Gilmore area this unit 

 has a maximum thickness of 400 feet, forming in most places the capping to the 



