450 G. F. LOUGHLIN 
accords with the structural relations in showing the fault to be an 
overthrust. 
Block faults: A striking difference between the faults just 
described and the undoubted normal, or block, faults of the district 
Fic. 4.—Geologic map of the Santaquin—Mount Nebo district showing overthrusts 
and block faults. /AR=pre-Cambrian granite, -€ =Cambrian quartzite; M = Missis- 
sippian and earlier limestones; T=Tertiary conglomerate and volcanics. Topographic 
base from the Manti sheet, United States Geological Survey. 
is that the latter are marked by longitudinal and, to a less degree, 
by transverse valleys, whereas those interpreted as overthrusts 
appear unrelated to topography. From Santaquin southward 
nearly to Green Canyon (see Fig. 4) the western side of the range is 
composed of parallel ridges separated by remarkably straight N.-S. 
canyons. The strata on opposite sides of these canyons are quite 
discordant. For example, just north of Wash Canyon (6 miles 
south of Santaquin), the upper Mississippian “‘intercalated series”’ 
