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head of Disenchantment bay and the northwest arm of 

 Russell fiord are all crystalline. All the north shore and 

 the eastern two-thirds of the south shore of Nunatak 

 fiord are also bordered by crystalline rocks — granite and 

 steeply-dipping gneiss, schist, slate and schistose conglome- 

 rate with stretched pebbles. 



These crystalline rocks abut abruptly against younger, 

 practically unmetamorphosed strata, both in Hidden Glacier 

 valley and on the south shore of Nunatak fiord. This 

 line of separation, interpreted as a fault, would, if con- 

 tinued, extend along the northwest arm of Russell fiord, on 

 one of whose shores the rocks are crystalline, whereas on the 

 other (the southwest), they are unmetamorphosed. 



From the area of crystalline rock to the foreland a 

 complex of strata, the Yakutat system of Russell, forms all 

 the mountains that border this part of the fiord. These 

 strata consist of thin-bedded black shales and sandstones, 

 thick beds of conglomerate, and a massive gray sandstone or 

 greywacke, which, in some parts at least, is an indurated 

 tuff. There are other beds in lesser amounts, and the 

 entire mass is complexly folded and faulted, both on a large 

 scale and in detail. Some faults and folds occur in all the 

 outcrops, and a score or more may appear in a single out- 

 crop a few square yards in area. The rocks are literally 

 crushed and kneaded. The Yakutat system is nearly 

 barren of fossils, and it has not been possible to determine 

 its age from those collected. There are some indications 

 that they are of Mesozoic age, and some that they are 

 older. Ulrich [32.] has classed them as Liassic. 



A third series of rocks was found in a few outcrops on 

 the west side of the Yakutat bay, 2 or 3 miles (3 to 5 km.) 

 from the mouth of Disenchantment bay and just outside 

 the mountain front. These rocks are mainly gray sand- 

 stones, clays, and carbonaceous shales, with a few thin 

 beds of lignite coal. They are tilted at a high angle, but 

 are not as complexly folded and faulted as the Yakutat 

 system, from which they are generally separated by a 

 fault. On the basis of fossil plants they are assigned to the 

 Pliocene epoch. 



Outside of the mountain front, as already stated, the 

 foreland of glacial gravels extends to the sea ; but near the 

 head of Russell fiord it is underlain by planated beds of the 

 Yakutat system and granitic rocks. No indurated rock 

 was found elsewhere in the foreland; though a low, butte- 

 like hill, that rises above it some distance from the moun- 

 tains, is evidently composed of rocks of the same system. 



