27 6 
Jones and Field — The Resurrection of the 
if not from the Miocene. Considering- the time that must have 
intervened between the excavation of the canyon and the rhy- 
olitic eruptions, the period of those eruptions must be pushed 
far back into the Tertiary period and these lavas are therefore 
much older than had been previously supposed. 
Fig. 2. Map of the Yellowstone and Lamar valleys modified from 
Holmes, plate XXX, 12th Annual Report, U. S. Geol. and Geophys. Surv., 
part, II, 1878. 
_A-B: Section showing distribution of glacial bowlders; C- 0 : Ocean 
divide ; E-F : Line of great fault ; G : Third Canyon ; H : Grand Canyon ; 
I: Tower Creek; K: Deep Creek (Jasper Creek of Holmes Report). 
A study of the map given by Holmes (Fig-. 2) to illustrate 
the distribution of the granite boulders in the neighborhood 
of the Yellowstone Valley suggested to us another possible 
explanation of some of the sediments in the canyon. The dis- 
tribution of the granite boulders is such that the ice appears to 
to i,._ 
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