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Show 194 GEOLOGY OF THE HIGH PLATEAUS. been uninterruptedly exposed to erosion, and it is by no means surprising that the average degradation should have been many hundreds or more than a thousand feet There is no evidence that they are old cones piled up of eruptive matter around local vents, but are unmistakably carved out of a mass of interstratified lava sheets and bedded fragments, like great cameos, and their altitudes notably augmented by local uplifting. The summit of Little Creek Peak gives a fine view of the surrounding country, though the altitude is insufficient to command the great expanse of the Markagunt to the southward, which is higher than the peak itself But north and east the prospect is excellent. As soon as the firs and spruces are cleared the Tushar is in full view to the northward, the grand pyramids of Belknap and Baldy stand out in splendid relief against the horizon, and the inclined plateau, whose summit they crown, is seen in detail. It may be recalled that this plateau slopes to the west, while the Markagunt slopes to the east. The Hurricane fault bounds the western front of the Markagunt, while the Tushar has a great fault upon its eastern front. The two plateaus gradually merge into each other through the intervening area of Dog Valley. The shifting of the displacement from the west front of the Markagunt to the east side of the Tushar is an interesting structural feature and worthy of a careful study, for it is often repeated in the Basin ranges, and constitutes one of the most important modifications of that type of structure. We may for present purposes regard the Tushar and Markagunt as a single block, of which the length is nearly 80 miles and the width a little more than 20. The southern portion is tilted eastward (Markagunt) and the northern portion is tilted westward, while the intervening or middle part is warped and otherwise flexed. Now if this great block were a simple warped surface, the middle portion would be synclinal. In reality it is an anticlinal area. An anticlinal axis leaves the Hurricane fault at a very acute angle, and crosses the block obliquely to the commencement of the Tushar fault. These structural features may be discerned distinctly from the summit of Little Creek Peak. Looking westward from the same point we behold in the foreground a scene eminently characteristic of the western border of the Markagunt. |