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Show UNCONFORMITY OF TEETIAEY AND CRETACEOUS. 157 tory of the unconformity is cleariy revealed. The monoclinal involves the whole Cretaceous system, but not the overlying Tertiary, and fixes the age of the disturbance between the close of the Laramie and the beginning of the Tertiary. The northern extension of the Water-Pocket flexure indicates a precisely similar movement coeval with the one already recited. This flexure disappears beneath volcanic accumulations at Thousand Lake Mountain. The summit of that mass consists of lava-capped Tertiary strata resting upon the Jurassic, while to the northeast of the mountain the Cretaceous beds are rolled up towards it monoclinally, with patches of level Eocene beds lying unconformably across their edges. An unconformity of Tertiary and Cretaceous is also laid open to view in Salina Canon. Around the flanks of the Markagunt Plateau many exposures of this unconformity are also seen. In truth, there appears to have been at this epoch a series of displacements having a north and south trend, breaking up the Mesozoic system into long blocks by well-defined monoclinal flexures, and the uplifted portions everywhere suffered denudation prior to the deposition of the Tertiary beds. On the other hand, very many of the contacts of the Eocene and Laramie beds are apparently conformable. This occurs wherever the older series escaped distortion, and throughout the central parts of the Plateau Province they usually did escape it. The great disturbances were for the most part localized in the vicinity of the old shore line, and only now and then extended far away from it. The disturbances, being alsp chiefly monoclinal flexures and faults, did not disturb very noticeably the horizontality of the strata except along the very narrow locus of the flexure itself. The existence of these unconformities indicates a lapse of time between the close of the period of deposition of the Laramie beds and the beginning of the local Eocene. Nor could this period have been of very trifling duration, for there are instances of extensive erosion of the Upper Cretaceous prior to the deposition of the earliest Tertiary. In the Aquarius Plateau and in Thousand Lake Mountain the Lower Eocene rests upon the Jurassic, and in the southern amphitheaters of the Aquarius the Tertiary lies across the beveled edges of the whole Cretaceous system. Whether such an occurrence may be construed as meaning a temporary emergence |