540 EEPOET UNITED STATES GEOLOGICAL SUEVEY. 



covered with the debris of the range to the westward, composed of lirde- 

 stone and quartzite pebbles. Underneath are the following beds : 



Yellow sands and conglomerates. 



Eed marls and sands. 



Purple sands and conglomerates. 



These beds are 500 to 600 feet thick, and dip slightly to the east- 

 ward. The conglomerates are composed of quartzite and hmestone 

 pebbles and bowlders, evidently derived from the range that lies to the 

 westward. Some of the hmestone pebbles contain indistinct fragments 

 of Carboniferous fossils. On the top of the plateau which these beds 

 form I found corals and a Sjpirifer in some of the pebbles. I think these 

 pebbles were derived from the weathering of some of the upper conglom- 

 erates. The bluff of bright colored conglomerates extends from the 

 Bitterroot to Lander Creek. Between Lander Creek and the main branch 

 of Marsh Creek the anticlinal again shows. On the ridge here Station 

 51 was located, on a hartl hmestone containing remains of a small gaste- 

 ropod that is probably of Jurassic age. As seen from this point, the 

 beds north of Marsh. Creek are more folded than was noticed at any point 

 south. The strike is about north 13° west. There were three anti- 

 clinals, all rather gentle; west of the most western the dip of the sand- 

 stones was 30°, and next to the Carboniferous Eange an angle of 20° wa s 

 noticed. Between these two points, however, the beds are nearly hori- 

 zontal, as shown in the section. The Wahsatch beds rise on the hills on 

 the east side, and remnants are seen resting on the upturned edges of 

 the sandstones on the west side. These sandstones are greenish-gray, 

 and laminated in character, l^o fossils were found in them. They have 

 been colored on the map to represent the Laramie Group, as the only 

 fossils found in their southern extension seem to indicate that as their 

 age. The area between the anticlinal and the Wyoming Eange is wider 

 from Lander Creek northward than southward. Marsh Creek rises op- 

 posite the head of McDougal's Creek, in a basin of sandstones which 

 present bluffs on the head of the latter. The di^iide between the two 

 streams is on the east side of the Wyoming Eange. Another case sim- 

 ilar to this occurs at the head^of a branch of John Day's Eiver; the di- 

 vide between them being some distance to the east of the range. An- 

 other case occurs farther north, on a much larger scale. This was just 

 north of our line, and will be the field of future exjiloration. 



WYOMING EANGE. 



I take up this range in this chapter inasmuch as the greater part of 

 its drainage is to the eastward into Green Eiver Basin. It is about 35 

 miles long in our district from Thompson's Pass to our north hne. Be- 

 yond the latter it reaches to the Gros Ventre Eange. The width is from 

 6 to 8 miles.- The peaks range in elevation from 10,000 to over 11,000 

 feet. Wyoming Peak, on which station 55 is located, is the highest peak, 

 having an elevation of 11,490 feet. 



Towards the Green Eiver Basin the range presents a rather abrupt 

 face, with basset edges of hmestone strata which dip to the westward 

 from 10° to 20°. These hmestones have been colored to represent the 

 Carboniferous, as only carboniferous fossils were foimd. There is an 

 exposure of from 2,000 to 8,000 feet of beds, and it is possible that the 

 lower portion ought to be referred to the Silurian or Devonian. 



At station 48 the following is a general section. 



