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Show 28 GEOLOGY OF THE HIGH PLATEAUS. babs, for the two districts have a common history, so far as relates to their more recent structure. The individual faults overlap, and both districts sympathized in the vertical movements. Indeed, the Hurricane and Eastern Kaibab faults form structure lines of the first magnitude in both districts, with no break in the continuity. The indications are unmistakable that the upliftings of the Kaibabs and High Plateaus were sensibly synchronous and formed one movement, and that any attempt to separate them would be to ignore their proper relations. The westernmost of the series is the Grand Wash fault. It crosses the Colorado at the lower end of the Grand Canon. Southward it curves gradually in its trend, and at the farthest point to which it has been traced its course is to the southeast. Northward from the river the curvature of the trend is still preserved though much less distinct, and its course is nearly due north. It runs out apparently about 35 miles from the river. Its maximum displacement is about 5,500 feet, and the lifted side forms the Sheavwits Plateau. Next in order comes the Hurricane fault. Its southern terminus south of the Colorado is unknown. It crosses the river just west of Mounts Trumbull and Logan, forming the Hurricane Ledge, and its course is nearly north, with a very slight swerving to the eastward. At the Grand Canon its displacement is about 1,800 feet, and this amount is maintained with little variation for about 40 miles north of the canon. Here its throw (to the west) rapidly increases. It becomes the western boundary of the great Markagunt upliftâ€"the southwesternmost of the High Plateaus, and is at the same time the boundary which sharply separates the Plateau Province from the Great Basin. Continuing on past the Mormon town, Cedar, and just before reaching Parowan, it suddenly swings eastnortheast, making almost a sharp angle. Thereafter it swings slowly back towards the north until it reaches the western flank of the Tushar, where its throw has much diminished. The precise point where it runs out is not known, since it is covered by basaltic eruptions, but it is not seen beyond the middle of the western flank of the Tushar. Its maximum throw is near Cedar, on the western flank of the Markagunt, where it reaches on an average, along 20 miles of its course, a displacement of about 5,000 feet. |