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276 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 rhyolitic 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.

[[image - map of Great Highland - Yellowstone Mts. - Chiefly Volcanic, showing major geographical features. Marked in several places with letters marking lines or points of interest.]]

[[image - geological cross section, showing fault line, labeled "A" on left side and "B" on right side]]

^[[Holmes' map and section 1878]]

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-O: 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 distribution of the granite boulders is such that the ice appears to ^[[have come from the north, i.e. from the "Granite Range"

to have come from the north, thus from the x range.]]