NORTHERN END OF TETON RANGE. 151 



TOPOGRAPHIC FEATURES. 



The region is about 10 miles wide from east to west, and 7 miles from 

 north to south, along the western side of Snake River Valley. The highest 

 point, Forellen Peak, is 9,700 feet in altitude, while others of 9,200 and 

 8,900 feet occur north of Berry Creek. The district is almost completely 

 transected by two deeply cut valleys, those of Owl and Berry creeks, 

 flowing into Snake River. The extreme western side of the mountains is 

 drained by Conant and Boone creeks, tributaries of Falls River. The sides 

 of these valleys are steep and exhibit frequent rock exposures. 



The valley of Owl Creek separates the mountain region situated within 

 the limits of the map (PI. XXIII) from the main range lying to the south. 

 The stream has cut a deep gorge at right angles to the uplift, heading in the 

 Carboniferous area south of Forellen Peak and on the slopes of Crimson 

 Peak, a prominent summit that reaches 10,300 feet on the flanks of the 

 range south of the forty-fourth parallel of latitude. That portion of 

 the gorge which is cut in the gneiss to a depth of nearly 3,000 feet shows 

 steep slopes much encumbered with the debris from the crest of the ridge. 

 Overlying the crystalline schists, the sedimentary series is well exposed to 

 the east. This trench, following as it does a line that crosses the strike 

 of the rocks, appears to be an old drainage way deflected by the rhyolite 

 capping which once covered this area, and it probably marks a g-ulch cut 

 along the contact between the rhyolite sheet and the underlying rocks, a 

 contact which undoubtedly crossed varying exposures, as the country was 

 much eroded before the outflow of the rhyolite. 



Berry Creek, which heads in the mountain amphitheater at the north 

 base of Crimson Peak and in the grassy valley lying south of Survey 

 Peak, flows with a general easterly course 4 or 5 miles, then turns abruptly 

 to the south to join Owl Creek, leaving what is clearly the old drainage 

 way across the sedimentary rocks, but which is now occupied by a 

 much diminished stream. It is believed to have been diverted by a small 

 lateral drainage which cut back until it robbed the stream of its head- 

 waters. Like Owl Creek, this stream heads in the Carboniferous area of 

 the western part of the mountains, crosses the upturned edges of the Survey 

 Peak rocks, flows through an open grassy valley cut in the crystalline 

 schists and across the basic breccias which conceal the Paleozoic beds of 



