ILLUSTRATIONS. 
Page. 
Plate I. Sketch map of a portion of western Arizona 9 
II. Temple Bar conglomerate at Temple Bar 16 
III. A, Signal Canyon, Aquarius Mountains, showing lava-capped gravel 
and sand filling; B, Chemeheuvis gravel near Bulls Head 22 
IV. A, Rhyolitic ash near Kingman; B, Detritus at the mouth of Deluge 
Wash 22 
V. Geologic sections 24 
VI. A, Castle-like erosional forms in Black Mesa at Union Pass; B, Basalt- 
capped gravels in Williams Canyon 26 
Vll. A, North wall of canyon in Grand Wash Trough; B, Mouth of Grand 
Canyon 30 
VIII. A, Temple Bar conglomerate resting upon older breccia near Tempte 
Bar; B, Entrance to Black Canyon 34 
IX. Map and section at south end of Pyramid Canyon, Colorado River... 38 
X. A, Colorado River and gravel-filled valley at Bulls Head rock; B, 
Tilted gravels in Sacramento Wash 40 
XI. Sacramento Valley at south end of Hualpai Mountains 52 
Fig . 1 . Sketch section across White Cliff Canyon 20 
2. East-west section across Big Sandy Valley 24 
3. Diagrammatic sections across Colorado River at mouth of Grand Canyon 
and in Iceberg Canyon 31 
4. Diagrammatic sections across Colorado River near Greggs Ferry, near 
Hualpai Wash , and in Virgin Canyon 34 
5. Diagrammatic sections across Colorado River at Temple Bar, at Virgin 
River, and in Boulder Canyon 35 
6. Diagrammatic sections across Colorado River near Las Vegas Wash, in 
Black Canyon, and at Little Round Island 37 
7. Map of a part of the Colorado Valley at the northern end of the Cotton- 
wood Valley 38 
8. Profiles across Colorado River at the southern end of Pyramid Canyon. . 40 
9. Diagrammatic sections across Colorado River at Pyramid Canyon, in the 
Mohave Valley, in the Needle Mountains, and at Williams River 42 
10. Map of Great Bend in Mohave Canyon '. 43 
1 1 . Relations of formations exposed in the Chemehuevis Valley 44 
12. Map and sections of a part of the Great Colorado Valley 46 
13. Map of a part of Chocolate Canyon 48 
14. Sketch section across Big Sandy Wash near mouth of Deluge Wash 51 
15. Sketch section across Big Sandy Wash at mouth of Trout Creek 51 
16. Section exposed in the south wall of Williams Canyon 54 
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