340 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



province was cut off during Middle Devonian, but became free about the beginning of Upper 

 Devonian time, when conditions became favorable for the dispersal and migration of such 

 forms as were adapted to it. Some of the species which had during Middle Devonian time 

 been confined to this northern basin spread southward and helped to give a distinctive char- 

 acter to the Upper Devonian fauna as we know it in the United States. This appears to be 

 the probable explanation of an association of species which upon casual examination seems 

 to afford contradictory evidence as to the age of the fauna. If correct, the horizon represented 

 is Middle Devonian. 



The Devonian limestone outcrops on both sides of the Salmontrout River near its mouth. 

 Brownish-colored shales overhe the limestone here and extend apparently to the top of the high 

 ridge lying to the south of the stream and represent a thickness of several hundred feet. No 

 fossils were found in these shales, but they are supposed to represent the Upper Devonian, 

 because their relation to the Devonian limestone is similar to that held by shales holding 

 Devonian fossils along the Yukon River. Carboniferous beds replace the Devonian outcrops 

 along the Porcupine about 1 mile below the Salmontrout River. These seem to be of Upper 

 Carboniferous age. Evidence of faulting which appears on the north bank of the river here 

 indicates that the Lower Carboniferous and perhaps a portion of the Upper Devonian may be 

 concealed by a fault. The horizon of the brown shale appears locally to be largely occupied 

 by beds of basalt representing old sea-bottom outflows during the Upper Devonian. 



The shale series which terminates the Devonian probably has a considerable thickness, 

 though no estimate can be made from the exposures mentioned, because the thickness exposed 

 to view is probably reduced by a fault lying to the southwest of the Salmontrout River. 



The shale horizon appears to be occupied locally by basalt flows of late Devonian age. 

 A considerable thickness of such beds, which are beheved to be of Devonian age, forms the 

 lower end of the Upper Ramparts. This rock is a close-grained dark-greenish to black rock, 

 showing bedding planes. These strike about north and south and dip east at about 40° for 

 nearly half a mile above Redgate. Near the top of this igneous series a belt of sedimentary 

 rocks is sandwiched into the basalts, showing the following beds: 



Section one-half mile above Redgate. 



Feet. 



Gray limestone 4 



Red and green shale 14 



Brecciated limestone with included masses of shale 8 



Light-gray limestone 35 



Red shale -. 30 



Two or three miles west of the Coleen River the basalts occur again. Here they overlie 

 a considerable thiclaiess of drab and pale-red shales. Black shales are interbedded with the 

 upper belt of basalt at this point. 



Q 8. PEEL RIVER. 



Peel River, flowing north from the Rocky Mountains of Yukon Territory to 

 the Mackenzie delta, traverses two canyons in folded black slates, which are alter- 

 nately thick and thin bedded and in places bituminous, and crystalline limestone, 

 which apparently underlies the slates. These strata are assigned by Camsell^^** 

 to the Devonian on the ground of their lithologic resemblance to the Devonian of 

 the Mackenzie Valley. 



<a-R 5. ENDICOTT RANGE. 



Nothing definite is known regarding the age of the pre-Carboniferous rocks of 

 the Endicott Range, but the Fickett " series" and the Stuver "series" may include 

 Devonian rocks, and the Bettles group is referred to the Devonian by Schrader, 

 who found fossils of Devonian or Carboniferous age in gravels of Chandalar River. 

 Brooks, ^"^'' however, regards the Bettles as possibly Silurian. 



