382 J. S. Diller — Bragdon formation. 



only a few miles, but farther along in the same horizon the 

 conglomerate comes in again. This top horizon of the Bragdon 

 will be noted at only two points. On Hirz Creek road the 

 top conglomerate is fine, but west of it a few hundred feet is 

 another that is coarse with fossiliferous Devonian pebbles. 

 The strata are all nearly vertical and for the most part well 

 exposed eastward to the shales full of Baird fossils. On the 

 divide about a mile and a half southwest of High Mountain 

 the characteristic conglomerates are well developed. Most 

 of them are iine, but one is coarse, with many pebbles of sand- 

 stone and some of fossiliferous Devonian limestone. These 

 lenses of Bragdon conglomerate are immediately and conform- 

 ably overlain by sandstone containing Baird fossils. An 

 observer cannot carefully study the contact of the Baird and 

 Bragdon from one end to the other without being convinced 

 on structural grounds alone that the Bragdon and Baird are 

 conformable and that the former is the older. 



As to the lower limit of the Bragdon, the matter is more com- 

 plex owing to the fact that the basement on which it rests is vari- 

 able, sometimes sedimentary rocks of Devonian age, but more 

 frequently volcanics. The best exposure of the Bragdon 

 resting on the Devonian is along Backbone Creek, three and 

 one-half miles north of Kennet, where over 800 feet of 

 Devonian shales and limestone** are overlain unconformably 

 by a thirty-foot bed of Bragdon conglomerate containing 

 fossiliferous Devonian fragments. To the east and west of 

 this locality the Bragdon beds overlap the Devonian to the vol- 

 canics, but in both directions there soon appear other patches of 

 Devonian lying between the Bragdon and the volcanics. Near- 

 by, on Little Sugar Loaf Creek, a small area of fossiliferous 

 Devonian is completely surrounded by Bragdon. Along this 

 portion of the Bragdon border the small areas of Devonian are 

 remnants left by pre-Bragdon erosion of a once continuous sheet 

 of Devonian and thus exposing the volcanic rocks which lie 

 beneath and were erupted before the Devonian sediments were 

 deposited. To the northward, in the vicinity of Hazel Creek, the 

 Devonian shales and limestone areas are more continuous 

 and may be traced for over ten miles along the western border 

 of the Bragdon. Although the contact is not well exposed, 

 the fact that the basal conglomerates of the Bragdon are at 

 least generally, if not everywhere, composed wholly of debris 

 from the Devonian sedimentary rocks, clearly indicates an 

 unconformity by erosion between them. 



It is in this portion of the pear-shaped Bragdon area that its 

 taxonomy is most evident and may be conveniently studied 

 along the trails from the McCloud to Castle Crag and Sims on 



* This Journal, vol. xv, p. 347. 



