OCR Text |
Show SEDIMENTAET BEDS OF THE WASATCH PLATEAU. 165 than those of the East Gunnison fault. Its position and relations are shown in the stereogram and in the sections above referred to. Between the East and West Gunnison faults is an uplift, qualifiedly tabular in form, which may be called the San Pete Plateau. Its northern end is separated from the base of Mount Nebo only by a canon, which emerges near the town of Nephi. Eastward it looks down upon San Pete Valley, -westward upon Juab Valley, which may be regarded as the northern continuation of Sevier Valley. Southward the plateau slopes slowly as far as the town of Gunnison, where it becomes the floor of the Sevier Valley. Its altitude is insufficient to warrant its admission as a member of the group of High Plateaus. Its general form may be illustrated as follows: If from a point situated about six miles south of Gunnison we travel north 30° east, our course would lead us up into San Pete Valley; if we travel north 30° west, it would lead us down the Juab Valley; if we travel due north, we shall ascend the easy slope of the plateau to its summit at its northern end. Its transverse structure is shown in the sections. Plate 'S; sections 1, 2, and 3. SEDIMENTARY BEDS COMPOSING THE WASATCH PLATEAU. The Wasatch Plateau consists of beds of Upper Cretaceous and early Tertiary age, the latter being correlated, as well as any lacustrine beds of the Rocky Mountain region can be, with the Lower Eocene. In the lowlands immediately adjoining are found, on the east the Lower Cretaceous, and on the west a singular occurrence of the Upper Jurassic. There is found also in the Sevier and San Pete Valleys, and in the low uplift between them, a series of strata of later age than the Tertiaries of the plateau, though from many considerations it appears that their age is with great probability early Tertiary and immediately subsequent to that of the strata upon which they rest. They are believed to be local deposits only, and to have accumulated here and there after the commencement of the general disturbance and uplifting which resulted in the drainage of the great Eocene lake. The principal Tertiary series is provisionally divided into two; the lower can be referred with confidence to the same horizons as those occu- |