Geology and Mineralogy. 311 



to head in a backbone of granite around Sixtymile Butte, which 

 is surrounded by quartzite-schists of the Birch Creek series. 

 These regions lie partly in American, partly in Canadian terri- 

 tory. 



The Canadian area has not been studied by American geolo- 

 gists, except in wayside observation along such routes of travel as 

 necessarily lay through it. The Canadian geologists, on the 

 other hand, did not in their earlier and published observations 

 recognize any subdivisions in the older rocks such as have been 

 made by Spurr. Hence it is not possible to attempt even a prox- 

 imate outline of the Canadian gold-bearing rock formations. 

 General geological data and local discoveries of gold-bearing 

 gravels indicate that the gold-bearing area is very large, and may 

 be roughly defined as reaching from Dease River to the boun- 

 dary, with a width of 200 to 300 miles or more. The recent enor- 

 mously rich discoveries have, however, been confined to a more 

 limited area around the Klondike and Stewart Rivers. It is 

 assumed that the east-west uplift of fundamental granite and 

 overlying rocks extends eastward into the Klondike district, and 

 that a second uplift in a southeasterly direction extends from 

 upper Fortymile Creek toward the valley of Stewart River. 



Spurr noted outcrops of the schistose quartzites of the Birch 

 Creek series for a large part of the distance from the mouth of 

 Fortymile Creek up to the junction of the Felly and the Lewes at 

 Fort Selkirk ; also granites at various points, in some cases schis- 

 tose like the fundamental granite, in others fresh and massive-like 

 intrusive granite. There were also occasional belts of marble 

 belonging to the Fortymile series, notably one 5 or 6 miles above 

 the mouth of Sixtymile Creek, not far from that of Stewart River. 

 These observations afford a rough section across the belt of crys- 

 talline schists mentioned by the Canadian geologists as stretch- 

 ing eastward and southeastward along the upper Pelly and 

 adjoining streams and across to the Frances River. Along the 

 eastern edge of the crystalline belt they also recognized rocks of 

 a general greenish color, made up largely of altered volcanic 

 rocks, which would answer to the description of the Rampart 

 series. Similar rocks were also noted at various points on the 

 Lewes above its junction with the Pelly, notably in the Seminow 

 Hills near the Big Salmon River, which may represent the de- 

 velopment of the Rampart series on the south flanks of the crys- 

 talline belt. . . . 



The hills surrounding the gulches of the Little Mynook and 

 Hunter Creeks, on the Lower Yukon, are formed of rocks of the 

 Rampart series. The bed-rocks are of diabase, tuffs, impure 

 shales, and quartzites, and in the bottoms of the gulches there is 

 from 10 to 20 feet of gravel. The gravel consists in part of 

 angular fragments of rocks that form the walls of the gulch, in 

 part of waterworn pebbles of Birch Creek schist, schistose gran- 

 ite, and other rocks. The gold is generally in rounded, bean- 

 shaped grains and nuggets, and less frequently in unworn par- 



