448 University of California Publications in Geology [Vol. 10 



the Greybull River and its tributaries, Sunshine Creek and Wood 

 River. Gooseberry Creek, to the south, drains a small area east of 

 the Wood River divide. Greybull River takes its source in the de- 

 pression between the Carter and Shoshone Mountains and pursues a 

 general northeasterly trend to its confluence with the Bighorn River 

 some seven miles above the town of Basin. Wood River rises high on 

 the northeastern flank of the Shoshone Mountains and flows in a north- 

 erly direction to its junction with the Greybull at the northern limit 

 of the map. Below the mouth of Wood River the Greybull has a 

 mean discharge of 300 to 400 second-feet. Gooseberry Creek takes its 

 headwaters from the lower slopes of the Shoshone Mountains and flows 

 easterly to meet the Bighorn River about ten miles south of Worland ; 

 within the limits of the map it is a small stream averaging ten feet 

 in width and one in depth. 



All the streams are at present actively engaged in cutting. The 

 veneer of fluviatile deposits upon the present flood plain, as upon the 

 elevated terraces, is comparatively thin, and at times of high water 

 the bedrock is laid bare along large portions of the stream-beds. In 

 Sect. 16, T. 47 N, Wood River is energetically attacking the steeply 

 dipping, resistant sands of the Benton, and has established a steep 

 declivity at this point in its course. Greybull River is now removing 

 material from the coal horizon of Erskine 's mine where the Mesaverde 

 formation passes gradually under the stream in a gentle syncline. 

 Gooseberry Creek flows on bedrock over a large part of its course. 

 The divides between the various catchment basins are yet essentially 

 unattac'ked ; the stream valleys are on the whole narrow and steep- 

 sided, though a vast amount of material has already been removed. 

 These facts, coupled with the absence of extensive graded tracts in 

 the stream courses, seem to indicate that the present geomorphic cycle 

 is in an early stage of maturity. There is little or no adjustment of 

 Sunshine or Rawhide Creeks to the structure of the Mesaverde beds ; 

 but the small perennial streams that drain the large area of Cody 

 shale north of Gooseberry Creek may be considered as essentially sub- 

 sequent. The major streams — Greybull River, Wood River, and Goose- 

 berry Creek — are undoubtedly to be classed as superimposed ; they 

 are totally out of accord with the structures of the older rocks. The 

 key to their history is to be found on Gooseberry Creek, where the 

 Wasatch beds are still unremoved over considerable areas. Goose- 

 berry Creek unquestionably originated as a consequent stream upon 

 a Tertiary terrane. As erosion progressed the folded Cretaceous rocks 

 were encountered below the Wasatch contact, but as the stream was 



