168 I. C. Russell — E.qjcdition to Mount St. Ellas. 



hills and the hills west of Icy bay and the southern portion of 

 the Samovar hills. North of Pinnacle pass there are rocks undis- 

 tinguishable lithogically from those about Yakutat bay. These 

 are exposed in Mount Owen and on each side of Dome pass ; 

 they also form the bold spurs about the immediate bases of 

 Mount Augusta, Mount Malaspina, and Mount St. Elias. In the 

 three instances last named these rocks dip beneath the schist 

 forming the crest of the St. Elias range, and it is probable that a 

 great overthrust there took place before the formation of the 

 faults to Avhich the present relief of the mountains is due. 



All the mountain sjjurs of Mount Cook, so far as is knoAvn, are 

 composed of sandstones and shales of the Yakutat series, with 

 the exception of the Pinnacle pass cliffs. Nearly all the debris 

 on the glaciers from Disenchantment bay to the Seward glacier, 

 and probably beyond, is derived from the rocks of this system. 

 The distribution of the rocks from Avhich the debris was derived 

 may be ascertained in a general way by tracing out the sources 

 of the glaciers. Medial moraines on the Hayden and Marvine 

 glaciers, however, have their sources on the northern slope of 

 Mount Cook, and are composed of gabbro and serpentine. These 

 rocks were not seen in place, and their relatio^i to the Yakutat 

 series can only be conjectured. 



Although the rocks of this system are stratified, it is impossi- 

 ble to determine their thickness, for the reason that they have 

 been greatly crushed and overthrust. This is well illustrated in 

 the Hitchcock range, which, as already explained, trends about 

 northeast and southwest, and is composed of strata of shale and 

 sandstone, having a nearly east-and-west strike and a uniform 

 dip toward the northeast. * Were the rocks in normal position 

 their thickness would be incredible. In addition to this nega- 

 tive evidence, there is the crushed condition of the strata to show 

 that movement has taken place all through their mass ; and in 

 a few instances thrust faults Avere distinguished, dipping north- 

 eastward at about the same angle as the lines of bedding. In 

 the crushing to Avhich the rocks have been subjected the shales 

 have suffered more than the sandstones, and have been draAvn 

 out into Avedge-shaped masses, the sharp edges of Avhich usually 

 point toAvard the northeast, Avhich is presumably the direction 

 from Avhich the crushing force acted. 



The hypothesis that the rocks in the St. Elias region have 

 been crushed and overthrust explains many otherwise inhar- 



