Colorado River Canyon

The southeastern boundary of the park for about 11 miles is the Colorado

River, from the bridge on which U.S. Highway 163 crosses the river to a

point upstream about half a mile below the mouth of Salt Wash.

Illuminated night float trips down part of this reach are run during the

summer, as noted on p. 16. Partly paved State Highway 128 follows the

southeast side of the river for about 30 miles to Dewey Bridge, then

goes northward about 15 miles to Cisco, where it connects with Highway

I-70.

The rocks of the Glen Canyon Group form the southernmost corner of the

park, as shown in figure 19. About 2 miles northeast of the bridge, we

cross the axis of the Courthouse syncline (fig. 9), which brings the

Navajo Sandstone down nearly to river level, as shown in figure 20. The

underlying Kayenta Formation is largely hidden by vegetation and

alluvial deposits in this view.

[Illustration: GLEN CANYON GROUP, forming southernmost point of

park, as viewed across the Colorado River from State Highway 128

half a mile above Moab bridge carrying U.S. Highway 163. Massive

sandstone forming about the lower third of cliff is the Wingate

Sandstone, darker thin-bedded sandstones and mudstones forming

middle section of cliff comprise the Kayenta Formation, upper cliff

is the lower part of the Navajo Sandstone. Note that the saltcedar

(tamarisk), which lines both banks of the river, is in full bloom.

(Fig. 19)]

[Illustration: NAVAJO SANDSTONE CLIFFS, bordering west bank of

Colorado River in Courthouse syncline, from State Highway 128 about

2 miles above the Moab bridge. Note rounded domes at top of cliff.

(Fig. 20)]

[Illustration: MOUTH OF SALT WASH, viewed across Colorado River from

point on State Highway 128, 11 miles above Moab bridge. Dark cliffs

on upper right and left are of Wingate Sandstone capped by thin

protective cover of resistant sandstone beds of the Kayenta

Formation. In background Wingate is overlain by entire Kayenta

Formation and lower part of the Navajo Sandstone. Wingate is

underlain to river level by weathered slope of the Chinle Formation.

Water in Salt Wash is largely backwater from the bankfull river;

actual flow in wash generally is much less but at times reaches

flood proportions. (Fig. 21)]

About 11 miles above the Moab bridge is the mouth of Salt Wash (fig. 1),

as viewed from State Highway 128. (See fig. 21.) Seventeen miles above

the bridge (east of area shown in fig. 1), we get an excellent view of

the southeast end of the highly faulted Cache Valley anticline, as shown

in figure 22. The background shown in the photograph formerly was the

easternmost part of the former monument, but when the monument graduated

to a park on November 16, 1971, this part of Cache Valley along with

most of Dry Mesa was withdrawn from the park and put under the

supervision of the Bureau of Land Management, also a part of the

Department of the Interior.

[Illustration: SOUTHEAST END OF FAULTED CACHE VALLEY ANTICLINE,

viewed northwestward across Colorado River from a point on State

Highway 128, 17 miles above Moab bridge. High cliff of Wingate

Sandstone on left is capped by thin protective layer of the Kayenta

Formation. About upper third of slope below base of cliff is the

Chinle Formation, below which is the Moenkopi Formation extending to

high-water level. Note bent and broken beds on right. (Fig. 22)]

As noted on page 16, part of “Run, Cougar, Run” was filmed just upstream

from the irrigated field in the foreground of figure 22, in a wide part

of the valley called Professor Valley (fig. 7). This valley and the

Richardson Amphitheater on the southeast side of the river were named

after a Professor Richardson who settled in the area in the 1880’s. The

long abandoned townsite of Richardson was 1¼ miles due east from the

point from which figure 22 was taken.

The Geologic Story of Arches National Park Geological Survey Bulletin 1393 · 第 18 / 32 题