FAULTING 523 



cappings of the upturned, eroded edges of the older formations in many 

 isolated patches. These relationships may be seen in the accompanying 

 map (figure 2). 



Faulting on the southern Flank 



The most persistent and important faul t of the south flank of the 

 Uintas, as noted above, crosses the east fork of the Du Chesne at the 

 first western tributary — a small creek locally called Iron creek. The 

 Iron Creek fault strikes east and west, and is strictly, in all this imme- 

 diate district, the dividing line between the great basal quartzite of the 

 Uinta mountains (King's "Weber") and the shales, sandstones, and 

 limestones of the later Paleozoic. The basal quartzite is not in sight 

 below the shales in ascending the stream to the fault zone, then sud- 

 denly it appears as the only rock even to the heights of the adjacent 

 mountain divides. A throw of at least 3,000 feet is therefore measur- 

 able at this point, since the difference in altitude between the gorges and 

 the ridges either side is at least that amount. On the plateau between 

 the Du Chesne and Rock creek, locally called " The Old man," this dis- 

 placement of the strata presents the phenomenon of bringing two promi- 

 nent quartzite beds together — that is, the basal (first) quartzite north of 

 the fault and the conglomeratic (second) quartzite lying immediately 

 below the gray limestone beds. On this plateau one may easily overlook 

 the break entirely, as the formation seems to be continuous, but in the 

 adjacent gorges the fault shows plainly. It seems possible that this 

 rather unusual juxtaposition* of the quartzites may account for the 

 neglect of 3,000 feet of shaly members of the series lying in this V-shaped 

 area in the river valleys. 



Toward the east the major fault line cuts higher up in the series, at 

 least above the carboniferous. There are other smaller faults and shat- 

 tered zones along which there has been vertical displacement. One case 

 of faulting noted by Powell f on the north side of the range showed a dis- 

 placement of 20,000 feet. It is estimated that the folding and associated 

 faulting has resulted in a total elevation of these sedimentary rocks, form- 

 ing the central portion of the Uintas, to approximately 30,000 feet above 



*On page 146 of volume i and page 313 of volume ii, Fortieth Parallel Reports, several fossils 

 gathered from the drab limestone of " Rhodes' spur" are noted in the following words : " From 

 the base of the formation, not far above the Weber beds, were obtained Chonetes granulifera, Mar- 

 tinia lineata, Syringopora, multattenuata, Zaphrentis, Lithostrotion, Enomphalus." When it is 

 pointed out that this is the very region where more than 3,000 feet of strata are in sight below the 

 •'drab limestone," and that their contact with the so-called "Weber" in turn is a fault line of 

 unknown displacement' the phrase "not far above the Weber" would seem to insist too strongly 

 on the unity of these formations. 



t J. W. Powell : Types of orographic structure. Am. Jour. Sci., vol. xii, p. 414. U.S. Geologica 1 

 and Geographical Survey, vol. vii. 



