PART III. 



SKETCH OF THE GEOLOGY OF THE ST. ELIAS 



REGION. 



General Features. 



Ill the preceding narrative, many references have been made 

 to the character of the rocks and to the geological structure of 

 the region explored. It was not practicable during the journey 

 to carry on detailed geological studies, but such facts as were 

 noted are of interest, for this reason, if for no other : they relate 

 to a country previously unknown. 



My reconnoissance enabled ixie to determine that there are 

 three well-defined formations in the St. Elias region. These are — 



1. The sandstones and shales about Yakutat bay and west- 

 ward along the foot of the mountain to Icy bay, named the Ya- 

 kutat system. 



2. A system of probably later date, composed of shale, con- 

 glomerate, limestone, sandstone, etc., best exposed in the cliffs 

 of Pinnacle pass and along the northern and western borders of 

 the Samovar hills, and named the Pinnacle system. 



3. The metamorphic rocks of the main St. Elias range, called 

 the St. Ellas schist. 



Yakutat System. 



The rocks of this system are of gray and brown sandstones and 

 nearly black shales. They are uniforjoi in lithological character 

 over a large area, and are usually greatly crushed and seamed. 

 So great has been the crushing to which they have been subjected 

 that it is difficult to work out a hand speoimen with fresh sur- 

 faces. Fragments broken out with a hammer are almost inva- 

 riably bounded by plains of previous crushing, and are usually 

 somewhat weathered. 



These rocks form the bold shores of Yakutat and Disenchant- 

 ment bays, and were the only rocks seen along our route from 

 Yakutat bay to Pinnacle pass. The whole of the Hitchcock 

 range is composed of rocks of this series, as are also the Chaix 



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