754 STEPHEN R. CAPPS 



for the tillite beds are lenticular in the cross-section exposed and 

 probably also down the dip. The uppermost tillite bed shown is, 

 however, known to persist along the strike for at least a mile, 

 though its thickness is variable. 



On North Fork of White River, about 6 miles east of the local- 

 ity here described, similar tillite beds are exposed in the canyon 

 of that stream and are there overlain by lava flows. The lava bed 

 shown near the base of the section and other lava flows interbedded 

 with the gravels and tilHte higher in the series, but not at this par- 

 ticular place, are brightly colored, reddish, scoriaceous lavas, like 

 the flows which are so generally distributed throughout the Wrangell 

 Mountains. They range in age from Tertiary to Recent, and 

 Mount Wrangell even now shows signs of mild activity. 



As already stated, the evidence seems fairly definite that the 

 last great ice advance in the White River valley was contempora- 

 neous with the Wisconsin stage of continental glaciation. Till left 

 by the ice during this advance is of widespread distribution in the 

 White River basin, and wherever observed is unconsolidated and 

 little oxidized. At one point at the edge of the Lime Creek gravel 

 flat, about 2^ miles from the locality of the section shown, the 

 unconsolidated till of the last ice advance was found lying uncon- 

 formably upon the upturned and glaciated edges of the older tillite, 

 proving definitely that the tillite series was laid down during a 

 glacial advance which antedated the last ice invasion. Further- 

 more, a long time-interval between the two glacial advances is 

 indicated by the induration of the tillite and by its deformation 

 since it was deposited. The physiographic evidence at hand also 

 goes to show that the older tillite was indurated and uptilted and 

 a mature topography eroded upon it before the last great glacier 

 remodeled the surface and left its morainal deposits. 



The tillite series here discussed is thought to have been laid 

 down near the oscillating edge of a glacier. The record shows 

 repeated advances, with deposits of morainal material, followed 

 by recessions during which the till was covered by outwash gravels 

 from the ice front, and one period during which finer sediments, 

 represented by the shales and sandstones, were laid down. These 

 materials may represent lake deposits. There were also occasional 



