170 /. 0. Rassell—Expediiioii to Mount St. Ellas. 



teristic appearance. The first important change in tlie geology 

 along the route traversed by us was met on reaching Pinnacle 

 pass. 



Pinnacle System. 



The rocks of this system, as already stated, are best exposed 

 in the great fault-scarp forming the northern wall of Pinnacle 

 pass. They are more varied in composition and have preserved 

 a better record of the conditions under which they were deposited 

 than the sandstones and shales of the Yakutat system. 



Only an approximate section of the rocks exj^osed in the Pin- 

 nacle-pass cliff was obtained. 



Sandstone and conglomerate weathering into spires . 

 Evenly bedded, sandy shale in thin layers 

 Coarse conglomerate ; bowlders of crystalline rock . 

 Thinly bedded, dark-colored sandstone and shale 

 Reddish conglomerate .... 



Light-gray sandstone, with thin, irregular coal seams 



Total . . . . , . 1,800 " 



There is also a compact, crystalline, gray limestone near tlie 

 upper portion of the series, which escaped notice in the cliffs. 

 At the end of the Pinnacle-pass cliffs, however, where the rocks 

 are turned northward by the great fault which decides the course 

 of the Seward glacier, and dip eastward at a high angle, the lime- 

 stone is well exposed, and has a thickness of about 50 feet. In 

 many places the surfaces of the layers are covered with fragments 

 of large Pecten shells. Associated with the limestone there are 

 reddish shales, much crushed and broken, and a peculiar con- 

 glomerate. The pebbles in the conglomerate are of many varie- 

 ties, and were observed at places along the Pinnacle pass cliffs. 

 Their most marked peculiarity lies in the fact that they have 

 been sheared by a movement in the rocks and sometimes broken 

 into several fragments which have been reunited, probably by 

 pressure. These faulted pebbles are characteristic of the strata 

 from which they were derived. Similar pebbles were afterward 

 obtained in the Marvine glacier near its junction with the Malas- 

 pina glacier, thus indicating that there are other outcrops of the 

 conglomerate about Mount Cook, near where the Marvine glacier 



