. Bulletin of the United States Geological Survey--Pre-Cambrian Geology of North America . B. MOUTH OF GRAND CANYON. DETAILS OF VALLEYS. 31. of a large crust block. It derives its name from Grand Wash, whichhere enters the Colorado from the north. Its western limb consists ofstrata of the tilted block, and its eastern limb is the fault scarp of theGrand Wash Cliffs. Not only are all the rock formations composing the Grand WashCliffs found in the tilted block in Iceberg Canyon, but strata youngerthan those in the cliffs are also present and pass beneath the riverlevel with an eastward dip of 60
. Bulletin of the United States Geological Survey--Pre-Cambrian Geology of North America . B. MOUTH OF GRAND CANYON. DETAILS OF VALLEYS. 31. of a large crust block. It derives its name from Grand Wash, whichhere enters the Colorado from the north. Its western limb consists ofstrata of the tilted block, and its eastern limb is the fault scarp of theGrand Wash Cliffs. Not only are all the rock formations composing the Grand WashCliffs found in the tilted block in Iceberg Canyon, but strata youngerthan those in the cliffs are also present and pass beneath the riverlevel with an eastward dip of 60° to 80°. Making no allowance fordip and considering only the altitude of corresponding strata in thewalls of Grand Canyon and in Iceberg Canyon, the downthrow at theGrand Wash fault isabout 5,000 feet. Thestrata of the blockpass beneath the riverlevel several mileswest of the fault the downthrow becomputed from thedip of the strata andthe distance from thefault line at whichthey pass beneath theriver, the displace-ment at Grand Washfault appears to beseveral times greaterthan the 5,000 feet inevidence at the sur-face. The m
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