JOSEPH PEAK. 47 



transverse drainage channel. This transverse drainage channel, which runs 

 northward to join Fan Creek, forms the natural boundary line between 

 the sedimentaries on the east and the andesite-porphyry on the west. The 

 sedimentary rocks are light-gray limestones, having a strike of S. 20° W., 

 and a dip of 10° W., which would carry the beds under the drift forming 

 the summit of the ridge to the west. The higher slopes to the east show 

 good exposures of the sedimentary rocks. A western spur of Joseph Peak 

 shows the following section of sedimentary rocks, the lowest bed exposed 

 being part of the Quadrant quartzites. 



Joseph Peal;, section. 

 5 Red beds, calcareous sandstones, etc. 



wT Feet ' 



ii Sandstone and limestones, fissile, gray, weathering brown-gray 25 



sandstone. I 



(.3 Limestone, gray, compact 10 



Teton ) 

 ,. . 5 2 Cherty sandstones and limestones 100 



Quadrant i 



., >1 Sandstones, quartzites, and interbedded gray limestones 300 



At the base of this spur the summit of the ridge is nearly flat and is 

 largely strewn with chert weathered out of the Teton limestones. The 

 beds here apparently dip SE. 10°, which takes them underneath Joseph 

 Peak. The cherty beds of the Teton series are here quite well exposed. 

 The chert occurs in both banded and nodular forms, and is so abundant 

 that the remaining material, which is generally sandstone, forms but a 

 minor feature. In seams and patches, however, the rock is free from chert, 

 and is then much more calcareous and contains fragments of fossils. North 

 of the spur from Joseph Peak the Teton limestone beds dip W. 8°, and 

 strike S. 8° E. Farther north the flat summit of the ridge is formed of a 

 fine-grained andesite-porphyry, whose rust-colored exposures much resem- 

 ble those of the sedimentary rocks. This rock forms the summit of a bold 

 cliff to the north. This cliff, which is about 500 feet high, shows, excellent 

 exposures of the Quadrant quartzites resting upon Madison limestones, 

 forming the channel of Fan Creek, and capped just beneath the andesite- 

 porphyry by the cherty beds of the Teton series. This exposure shows a 

 total thickness of 350 feet of Quadrant quartzite and 125 feet of the Teton 

 limestone. The character of the cherty limestones varies from a dove- 

 colored, nearly pure limestone to a granular brown sandstone which is not 



