162 ALASKA AND ITS MINERAL RESOURCES 



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

 be roughly defined as reaching from Dease river to the bound- 

 ary, 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 river districts, 

 over which it has been possible to extend, with a reasonable de- 

 gree of probability, the colors indicated on the map for adjoin- 

 ing American areas. Thus 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 south- 

 easterly 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 Pelly and the Lewes 

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

 schistose like the fundamental granite, in others fresh and mass- 

 ive like intrusive granite. There were also occasional belts of 

 marble belonging to the Fortymile series, notably one five or six 

 miles above the mouth of Sixtymile creek, not far from that of 

 Stewart river. These observations afford a rough section across 

 the belt of crystalline schists mentioned by the Canadian geol- 

 ogists as stretching 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 vol- 

 canic rocks, which would answer to the description of the Ram- 

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

 the Lewes above its junction with the Pelly, notably in the Sem-^ 

 inow hills near the Big Salmon river, which may represent the 

 development of the Rampart series on the south flanks of the 

 crystalline belt. 



PLACER OR DETRITAL DEPOSITS 



The extraordinarily rich placer deposits of the gulches tribu- 

 tary to the Klondike river above Dawson, and of similar gulches 

 of the nearby Indian creek and Stewart river, have been so re- 

 cently opened that no detailed geological description of these 

 localities has yet been received. In his report, however, Spurr 

 had shown that the strike of the gold-bearing rocks in the Forty- 

 mile district and the exposures observed along the Yukon indi- 

 cated that their gold must have been derived from the same 



