i 



DEVONIAN 287 



feet below the limestone described, shows a series of slates and phyllites 

 intimately intermingled with greenstones, some of which may be intru- 

 sive, but all appear to be of the same types as those described above. 

 These rocks are intensely folded and shattered. It is not impossible that 

 these phyllites may represent a part of the older schist series, but their 

 association with the Devonian is so intimate as to lead to their assign- 

 ment to that system. These phyllites and some greenstones are exposed 

 for about a mile down the river, and then, after passing a belt without 

 any exposures, an area of black and gray shales with some feld spathic 

 sandstones is encountered. These beds are thrown up into l)road, open 

 folds striking about east and west, with dips of from 20 to 50 degrees. 

 Careful search was rewarded by only a few fossils, but sufficient to iden- 

 tify the beds as Devonian. It must be confessed that the evidence that 

 the greenstones, with associated limestones and phyllites, belong to the 

 same terrains as the shales and sandstones is by no means conclusive. 

 Similar greenstones, however, in the other parts of the province are 

 known to be of Devonian age. 



Xear the big bend 6 miles below Eagle (see map, figure 2), a belt of 

 chert conglomerate and sandstone, with some shale, here assigned to the 

 Carboniferous, crosses the river. These rocks are here correlated with 

 the Nation Eiver formation, but it is not impossible that they may be of 

 Devonian age, in which case they represent a phase of the Devonian un- 

 known in any other part of the section here described, or may even be of 

 Tertiary age. The relation of these Devonian shales to this conglom- 

 erate series could not be determined, but the general distribution of tho 

 two formations suggests that tliey are separated by a fault. Half a mile 

 below the last outcrop of the conglomerate there is a second belt of Devo- 

 nian, here made of black siliceous slates carrying considerable pyrite, suc- 

 ceeded by black clay shales and slates. These carry a few Devonian fos- 

 sils and merge upward into a shale limestone series which yielded 

 Carboniferous (Jlississippian) invertebrates and here called the Calico 

 Bluff formation. The shales of this Upper Devonian horizon have a 

 rather uniform dip downstream, with a thickness of at least 1,000 feet. 

 The lower and more siliceous beds of this horizon are much jointed, two 

 systems being recognizable, one parallel and one at right angles to bed- 

 ding. A diabase dike was noted cutting these slates at right angles to the 

 bedding. 



Fossils are extremely rare in the shale series which forms the highest 

 divisions of the Devonian. Below Eagle about 5 miles, on the west bank 

 of the Yukon, a single specimen of a lamelli-branch was found in the 

 drab-colored Upper Devonian shales. Although fragmentary, it appears 



XXVIII— Bull. Geol. Soc. Am., Vol. 19, 1907 



