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Show 32 GEOLOGY OF THE HIGH PLATEAUS. direction; i. e., the throw north of the zero point is to the east while south of this point it is to the west. The fault with its throw reversed now continues northward, crossing the lower end of San Pete Valley, and becomes the eastern wall of the San Pete Plateau, its shear increasing until it reaches nearly to Mount Nebo. It has not been traced farther, but where it has last been verified it is still in considerable force. The length of this displacement, so far as now known, is nearly 220 miles. It forms the western fronts of the Paunsagunt and Sevier Plateaus and the eastern front of the San Pete Plateau. The Western Kaibab fault is the fifth great displacement. It is supposed at its southern extension across the Grand Canon to unite with the Eastern Kaibab fault, as it is known to do at its northern end at Paria, about 40 miles north of the head of Marble Canon. Its trend describes a large bow, of which the Eastern Kaibab fault is the chord. Between them the Kaibab Plateau has been uplifted. Through the portions immediately north of the Grand Canon it is stepped, but the steps unite into a true monoclinal flexure opposite the middle of the Plateau. Towards the north it gradually dies out, and near the junction with the Eastern Kaibab displacement it is but a gentle monoclinal swell and hardly perceptible. The Eastern Kaibab fault is the longest line of displacement of which I have ever heard. It comes up out of unknown regions in Arizona from the vicinity of the San Francisco Mountain, and appears near the mouth of the Little Colorado River as a double displacement, but probably considerably complicated.* The displacement has two parallel branches, which appear to be faults where they cross the Colorado, but about 10 miles northward they gradually pass into two beautiful monoclinal flexures, the strata being unbroken, except by erosion at the surface. At House Rock Valley the two flexures merge into one, which continues northward past Paria, trending first northnortheast, but gradually swinging in a curve around to the northwest, always preserving its true monoclinal form. As it approaches Table Cliff, it dwindles as if about to die out; but opposite the southwest angle * Professor Powell is probably the only geologist who has seen these faults in this locality. The place is a terrible one to reach unless by boats through the entire length of the Marble Canon, and even then the approach is formidable. He would be a bold mp,n who should endeavor to reach the locality from above. |