68 RECONNAISSANCE OF PART OF WESTERN ARIZONA. 
CORRELATIONS. 
Explanatory statements. — Although no definite correlations can be 
made between the products of deposition and erosion of this and other 
regions, there are certain presumptions worthy of consideration. The 
succession of Quaternary events in western Arizona is similar to that 
of the Lake Bonneville and other inland regions, and the long epochs 
of erosion and thick deposits of sediment represent comparable lengths 
of time for each region. Western Arizona is a part of the great area 
of western America which underwent extensive changes of elevation 
during Tertiary and Quaternary time, the various epochs of which 
were recorded in marine deposition and erosion along the Pacific 
coast. Since western Arizona is a part of the Pacific drainage area, 
although far inland, it is presumably true that the great epochs of 
the coast correspond in some measure with the great epochs of the 
interior, inasmuch as the thick marine deposits must represent long 
periods of erosion of the land areas. 
(Comparison with. Lake Bonneville history. — In his summary of the 
history of the Lake Bonneville oscillations Gilbert a enumerates the 
following events, given in order from oldest to youngest: 
1. Erosion. Gilbert says: "This we may call the pre-Bonneville 
low-water epoch. It was of great duration compared with those 
enumerated below." 
2. Deposition. First Bonneville epoch of high water; deposits of 
Yellow Clay. This epoch is estimated (p. 316) as being five times 
as long as the second epoch of deposition (4). 
3. Erosion. Represented by unconformity and by alluvial deposits. 
The duration is estimated (p. 316) as greater than that of the final 
retreat of the water (5). 
4. Deposition. Second Bonneville epoch of high water; deposit of 
White Marl. 
5. Final retreat of water, intermittently, to present stage. 
The thickness of the Lake Bonneville beds was not known at the 
time of Gilbert's writings, nor is their maximum thickness yet 
determined. Boutwell b has shown that a 2,000-foot well at the 
eastern margin of Salt Lake, near Farmington (altitude 4,231 feet), 
does not penetrate through the fragmental beds. A similar thickness 
of sediments has recently been found in a deep boring at Neels, Utah 
(altitude 4,621 feet), a station on the San Pedro, Los Angeles and 
Salt Lake Railroad east of Sevier Lake. The well, which was com- 
pleted in 1906, is 1,998 feet deep and penetrates 1,944 feet of sedi- 
mentary matter before reaching bed rock, which is granite. 
a Gilbert, G. K., Lake Bonneville: Mon. U. S. Geol. Survey, vol. 1, 1890, p. 259. 
i> Boutwell, J. M., Oil and asphalt prospects in Salt Lake basin: Bull. U.S. Geol. Survey No. 260, 
1904, p. 471. 
