330 E. M. KINDLE RECONNAISSANCE OF PORCUPINE VALLEY 



to the Devonian limestone is similar to that held hj shales holding Devo- 

 nian fossils along the Yukon river. Carboniferous beds replace the 

 Devonian outcrops along the Porcupine about 1 mile below the Salmon- 

 trout 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 

 ma}^ be concealed b}'- a fault. The horizon of the brown shale appeal/ 

 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 consid- 

 erable 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 believed 

 to l3e of Devonian age, forms the lower end of the Upper Eamparts. 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 

 degrees for nearly half a mile above Eedgate. Near the top of this 

 igneous series a belt of sedimentary rocks is sandwiched into the basalts, 

 showing the following beds : 



Tl 



I 



i 



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 3 miles west of the Coleen river the basalts occur again. Here 

 they overlie a considerable thickness of drab and pale red shales. Black 

 shales are interbedded with the upper belt of basalt at this point. 



I 



CARBONIFEROUS SHALES AND LIMESTONES 



The outcrops of the Devonian limestone below the Salmontrout river 

 are followed immediately in the exposures of the river bank by outcrop- 

 ping Carboniferous shales. As a result of faulting, however, these expo- 

 sures appear to represent an Upper Carboniferous horizon. 



The Lower Carboniferous is represented by a series of shales and thin 

 beds of limestone, which outcrop between the lower end of the Lower 

 Eamparts and the Indian village. The character of the lowest beds of 





I 



