158 GEOLOGY OF THE YELLOWSTONE NATIONAL PARK. 



summit of the mountain south of Owl Creek, steeply upturned limestones 

 dip 80° W. and appear to be continuous with those, to be described, west of 

 the summit of Forellen Peak. Directly west of them, on the divide south 

 of the head of Owl Creek, massive limestone abuts against them with a low 

 easterly dip. These are the eastern portion of a flat anticlinal arch, whose 

 axis trends north along the western side of the amphitheater at the head of 

 Owl Creek. The western portion, with slight westerly clip, forms the ridge 

 between the headwaters of Owl and Conant creeks, the most northerly point 

 of which is Crimson Peak. 



crimson Peak. — Here the strata strike S. 50° W. and dip 7° NW. The 

 dips farther down the northwest spurs vary from 7° to 10° in the same 

 general direction. The red color of the summit, which is so prominent 

 when the mountain is seen from a distance, is due to the red magnesian 

 streaks and patches which occur in the higher beds of the Carboniferous 

 limestones. The summit of the peak, which is 10,300 feet above sea 

 level, shows good exposures of the white Quadrant quartzites, the rocks 

 weathering in great cubical blocks; being of very compact texture, they 

 resist erosive agencies and are in striking contrast to the same series 

 exposed near the junction of Owl and Berry creeks. Fossils collected from 

 the northeastern spur of the mountain prove to be of lower Carboniferous 

 age. Farther down the spur, on the saddle of the divide southwest of 

 Forellen Peak, a horizon of fossiliferous limestone, carrying' peculiar con- 

 cretions of chert, occurs above a brown arenaceous bed that is correlated 

 lithologically and by its stratigraphic position with the Devonian of the 

 Gallatin section. This sandy limestone, which is believed to correspond to 

 the Three Forks limestone, is underlain by fine-grained and dense gray 

 limestone, whose peculiar rough, pitted, and guttered surface makes it a 

 readily distinguishable horizon. This bed corresponds to the Jefferson 

 limestone of the Gallatin Range. These strata continue northward along 

 the western slope of Forellen Peak, having a low dip to the west. They 

 adjoin the nearly vertical limestones that have been faulted against the 

 gneiss in the same manner as in the mountain south of Owl Creek. 



Foreiien peak. — Nearly vertical limestones form the western summit of For- 

 ellen Peak and the steep narrow spur down its northern flank. The beds 

 forming the summit of the peak are Carboniferous, and 100 feet below 

 them stratigraphically is the dark-gray massive limestone, weathering with 



