380 



INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



The section of Pennsylvanian and Permian beds exposed in Big Cottonwood 

 Canyon, southeast of Salt Lake City, is described in detail by Boutwell,*^ who gives 

 the following section: 

 ■Columnar section of 'portion of Carboniferous in Big Cottonwood Canyon, Wasatch Range, Utah. 



L 11. BLUE MOUNTAINS, OREGON. 



Lindgren^*" refers certain clay slates, siliceous argillites, and limestones of the 

 Blue Mountains in Oregon doubtfully to the Carboniferous : 



Rocks referred to the Paleozoic system occupy a large area in the lower Burnt River region, 

 about Pleasant Valley, in the southern Elkhorn Range, and on the headwaters of Burnt River 

 and Granite Creek. Smaller isolated areas of clay slate, inclosed in diorites, diabases, and 

 serpentines, also occur near Susanville, in the Quartzburg district, and near Canyon. There is 

 no clue to the age of these, but they are believed to belong to the * * * Paleozoic series. The 

 prevaihng rocks through the whole of this large sedimentary area are dark and very fine grained, 

 ranging from cherts to siliceous argillites and ordinary clay slates. A large proportion of the 

 sediments show no distinct stratification in ordinary outcrops, but in thin sections the carbo- 

 naceous streaks which indicate the planes of deposition are readily recognized. In many places, 

 however, the rocks are normal clay slates of fairly fissile character. 



********* 



The only place where fossils were found is near the Bonanza mine, at VT'interviUe, where 

 round crinoid stems occur in a small mass of crystalline limestone. The other limestone lenses 

 in the series, though carefully examined, yielded no fossils. Round crinoid stems are most 

 common in Paleozoic roclis ; taken in consideration with the fact that the series as a whole has 

 a distinctly older appearance than the Triassic of Eagle Creek, from which it is also petro- 

 graphically very difl'erent, we may with some confidence refer it to the Paleozoic and possibly 



