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Show SOUTHERN TERMINATIONâ€"MIDGET'S CREST 181 superposed masses of volcanic beds resting upon the great conglomerate. Here the faulted wall of the range swings around to the southwestward and rapidly dies out. (See stereogram.) The lofty crest at the southern end of the Tushar has been named Midget's Crest, and it presents to the southeast three bold salients, standing about 5,600 feet above Circle Valley, which lies at the base of its great spurs east-northeast. Its absolute altitude is about 11,600 feet. It is a volcanic mass, built by the accumulation of andesitic, trachytic, and basaltic sheets. The three salients are from 1,400 to 1,600 feet higher than the summit of the conglomerate cliff to the north of them and their superior eminence is due to this accumulation of lavas. The conglomerate passes beneath them though its outcrop is masked by the talus. The sheets which compose Midget's Crest belong to a later period than those which occupy the central part of the Tushar range, and which were broken down to form the great conglomerate. Coulees of the same period are found north of this crest, upon the summit of the tabular part of the Tushar, where they are mainly trachytic. Upon the extreme summit of the southern crest lies a true basalt, highly vesicular upon its surface, and the first impression is that it is a comparatively recent eruptionâ€"Post-Pliocene or Quaternaryâ€"the rocks on which it rests being certainly very much older. It is of small expanse and thickness and is abruptly cut off at the crest-line of the ridge. Its origin cannot easily be conjectured. There are no indications of a vent in the vicinity and, notwithstanding the freshness of its appearance, it may be as old as early Pliocene. But the beds on which it lies are less doubtful. They face southeastwardly, forming the salients already mentioned, and have been wasted greatly by the general degradation. When the period of dislocation and uplifting set, in they extended as far to southeast as the principal fault which runs around this angle of the plateau with a throw of about 3,500 to 4,000 feet, and the entire mass between the crest-line and the fault has been denuded to a corresponding depth. The origin of the lavas I believe to have been to the southeast and east of the ridge in the vicinity of the faults, where evidences of great contortion and considerable chaos are still visible, and where rocks apparently identical with those upon the summit of the table and near the |
