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Show SEDIMENTABY BEDS OF THE WASATCH PLATEAU. 167 Series No. 2 (Tertiary), section No. 7 B: Feet. (a) Cream and gray limestone, containing a few fish-scales 5 bed of chert at top.. 300 (b) Greenish calcareous shale............................................... 300 (c) Pale red marly shale.................................................... 300 900 These beds are assigned provisionally to the Lower Green River epoch. Unlike the series below them, they cannot be directly connected with the strata lying at the base of the Uintas, nor are their fossils a satisfactory guide to a decisive correlation, though the presence of fishes resembling those of the Green River beds might be regarded as indicating such a relation. They have not, however, been identified as belonging to the same species as those of the latter formations. The beds in question are found only in the Sevier and San Pete Valleys, in the uplift between them, and extending a short distance up the great monoclinal flanking the west side of the Wasatch Plateau. That they formerly extended over that plateau, and for an indefinite distance eastward, is very probable. In this portion of Utah they are the last lingering remnants of a series which was nearly and in many large areas quite the last to be deposited and the first to be attacked by the general process of degradation which has swept away such vast masses of strata. From the summit of the Wasatch Plateau this whole group of beds has been eroded and about 300 feet of the Bitter Creek beds immediately beneath, and this amount of denudation is probably the minimum of the whole Southern Plateau Province, except where the sedimentary beds have been protected by volcanic rock or have enjoyed uninterrupted protection in gravel-covered valleys between great uplifts. The uppermost series of Tertiary beds has been alluded to as consisting probably of a series of local deposits accumulated after the general upward movement of the whole Plateau Province had commenced, though it seems probable that this movement was then in its earlier stages. The beds contain fossils very similar and perhaps in some cases identical with the species of Planorhis Physa Helix (?), and Viviparus, which are found in the series upon which they rest. Pathologically they are much more variable. $ome of them are conglomerates, which are apparently of alluvial origin, and none of them are found to be continuous over a large area. |