286 BROOKS AND KINDLE PALEOZOIC ROCKS OF UPPER YUKON 



kenzie Elver district, although "2,000 feet or more of grayish limestone 

 interstratified with dolomites," lying below the beds with Middle Devo- 

 nian fossils, are referred provisionally to the Devonian by McConnell.^" 

 In the absence of paleontologic evidence of the age of this dolomitic 

 series, it Avould appear probable that it is of Silurian age and should be 

 correlated with a series of somewhat similar character on the Porcupine 

 river which is shown to be of Silurian age in this paper. 



In southeastern Alaska Lower, Middle, and Upper Devonian faunas 

 have been recognized by Kindle.*^ Neither the faunas nor the lithologic 

 members of the section show any close resemblance, however, to those of 

 the Upper Yukon Devonian section. 



The slates and shales, with subordinate sandstone masses and some 

 greenstones, which outcrop along the Yukon between Eagle and Calico 

 bluff, form a second group of Devonian rocks. The upper part of this 

 succession, made up of black shale and slate, lies immediately underneath 

 and conformable to the limestones and shales of the Calico BlufE forma- 

 tion of Lower Carboniferous age. It is probable, therefore, that all of 

 the rocks in this group should be referred to the Upper Devonian. The 

 few fossils which have been found in the rocks of this group bear out this 

 point of view. 



Immediately northwest of the town of Eagle is a high ridge trending 

 about east and west. Eagle peak, the eastern end of this ridge, is made 

 up largely of greenstone, which outcrops in numerous small cliffs along 

 the slope. The greenstone is both massive and schistose, the latter phase 

 occurring along shear zones. The massive form, which Avas studied by 

 Prindle a few miles to the westward, appears to be a basalt in which the 

 schistose phases are made up entirely of secondary minerals, among which 

 chlorite dominates. At this locality no tuffs were found, but Prindle re- 

 ports some tufaceous rocks near the International boundary on what 

 appears to be an eastern extension of this belt. 



On the southern slope of Eagle peak, and half way between the river 

 and the summit, a bed of shaly siliceous limestone, less than a hundred 

 feet thick, Avas observed, and Prindle reports similar occurrences a iew 

 miles to the westward. The presence of this imaltered limestone in the 

 midst of the igneous rock indicates that the latter Avere surface flows 

 rather than intrusions, and suggests that the volcanic outpourings AA'ere 

 submarine rather than terrestrial. 



The section exposed along the river, on the other hand, about 1,500 



1 



^ Geological Survey of Cauada, Contributions to Paleontology, vo). 1, part 3, 1891, 

 p. 250. 



« Journal of Geology, vol. 15, 1907, pp. 324-330. 



