438 G. F. LOUGHLIN 
Fortieth Parallel Survey, and that on the Park City mining dis- 
trict by Boutwell. Mr. F. S. Emmons, of the Fortieth Parallel 
Survey,, mapped the geology of the Wasatch Mountains from 
Provo Peaks northward, and his report gives brief mention of 
Mount Nebo 25 miles farther south—the highest and southernmost 
peak of the range. Mr. Emmons had only three weeks for his 
entire work in the Wasatch Mountains, and the amount of ground 
covered and the great quantity of data gathered by him in that 
time are indeed wonderful. It is only to be expected that his 
traverses did not lead him to all the places where the clues to stratig- 
raphy and structure were exposed, and that in the absence of those 
clues certain evidence could not be finally interpreted. It is, 
however, a relatively easy matter for one aided by the Fortieth 
Parallel map to investigate certain special problems and to find 
evidence which modifies the interpretations originally given. 
Boutwell has done considerable work in the country around the 
Cottonwood and American Fork districts,? and has thrown much 
light on the geology of both the igneous and sedimentary rocks; 
but his published detailed work on the latter deals chiefly with 
formations stratigraphically higher than those considered here, 
and the detailed descriptions of structure are confined to an area 
farther east than that visited by the writer. Boutwell, however, 
was the first to recognize overthrust faulting in the Wasatch 
Mountains.* 
Blackwelder in rg104 made some interesting contributions to our 
knowledge of the northern Wasatch Mountains, eliminating the 
“Ogden (Devonian)”’ quartzite of the Fortieth Parallel Survey 
and discovering several great overthrust faults. He also examined 
the Big Cottonwood Canyon section and found an unconformity in 
the great quartzite series, correlating the overlying 1,500 ft. of the 
quartzite as Cambrian and the underlying 10,500 ft. as Algonkian. 
«U.S. Geol. Explor. of the Fortieth Parallel, 11 (1877), 342-66. . 
2J. M. Boutwell, “‘Geology and Ore Deposits of the Park City District, Utah,” 
Prof. Paper 77, U.S. Geol. Survey, 1912. 
3 J. M. Boutwell, “Stratigraphy and Structure of the Park City Mining District, 
Utah,” Jour. Geol., XV (1907), 456-57- 
4. Blackwelder, ‘‘ New Light on the Geology of the Wasatch Mountains, Utah,” 
Bull. Geol. Soc. of America, XXI (1910), 517-42. 
