F. J. Alcock — The Athabaska Series. 27 



Conglomerates are in greatest abundance towards the 

 base of the formation, in many places resting uncon- 

 formably on the truncated edges of an older quartzite 

 series. The bowlders are well rounded and range in 

 size np to 18 inches in diameter. They consist of quartz- 

 ite, granite-gneiss, vein quartz, and a few small bowlders 

 of iron formation. Where the series rests on quartzite, 

 this forms the dominant type of bowlder, and where it 

 rests on granite, the latter is the most abundant type. 

 The conglomerates show but a limited amount of sorting, 

 bowlders of various sizes being associated together in 

 a sandstone matrix. East of Beaverlodge lake alterna- 

 tions of fine red sandstone and conglomeratic beds form 

 the lower portion of the series. 



The finer-grained portions of the series consist of 

 sandstone and arkose. Portions of the former show in- 

 cipient quartz enlargements and approach a true quartz- 

 ite. In places considerable quantities of feldspar are 

 present, and the rock becomes a true arkose. North of 

 the Beaverlodge lake this variety becomes a red, hard, 

 well-cemented, thick-bedded rock. A characteristic fea- 

 ture seen in nearly every outcrop is the presence of well- 

 rounded, quartz pebbles averaging about an inch in 

 diameter, which are found sparingly throughout the 

 series. In sonde massive varieties of the rock they are 

 abundant enough to mark the bedding planes. In places 

 the rock is so well cemented that it breaks directly across 

 these quartz pebbles. 



A local outcrop referred to this series consists of a 

 red breccia made up of angular fragments of quartzite 

 firmly cemented by a fine-grained matrix consisting of 

 quartz, iron ore, chalcedony and sericite. Some of the 

 smaller quartz particles are rounded, but the majority are 

 subangular and were clearly not transported far. 



West of Beaverlodge lake, the series forms hills, which 

 rise to a height of 200 feet above the lake. The top of 

 these hills consist of diabase and basalt outcropping in 

 bands parallel to the strike of the series. The coarse- 

 grained diabase has the relationship of intrusive sheets, 

 but two of the bands consist of amygdaloidal basalt rep- 

 resenting surface flows. The amygdules consist of cal- 

 cite and vary up to 1V 2 inches in diameter. In the Doo- 

 baunt area Mr. Tyrrell found dikes and masses of both 

 acid and basic eruptives, diabases and quartz-porphyries, 

 traversing the sandstone and conglomerate beds of this 

 series. 



