. Report of the geological exploration of the fortieth parallel . ps, and these in turn by of the city, on the eastern side of the river, is a remarkable seriesof hills stretching back four or five miles from the river, appropriatelycalled by Powell the Alcove Ridges, from their singular mode of river cliffs are here cut by transverse ravines, bold headlands project-ing against the river bank with almost vertical foces. The exceedinglyfine characteristic shaly structure of the upper part of the group is alsowell shown in Bitter Creek Valley, in a railway cut The platea
. Report of the geological exploration of the fortieth parallel . ps, and these in turn by of the city, on the eastern side of the river, is a remarkable seriesof hills stretching back four or five miles from the river, appropriatelycalled by Powell the Alcove Ridges, from their singular mode of river cliffs are here cut by transverse ravines, bold headlands project-ing against the river bank with almost vertical foces. The exceedinglyfine characteristic shaly structure of the upper part of the group is alsowell shown in Bitter Creek Valley, in a railway cut The plateau tothe north of the railway presents to the south and east a bluff from800 to 1,000 feet high. All these strata dip at gentle, almost imper-ceptible angles to the west toward a middle line of depression, in theBridger Basin. At a short distance west of Green River the calcareousshales pass, with apparently a slight unconformity, beneath the softer bedsof the overlying group. As exposed by the river-cut and the Alcove Ridges, TJ S^ PLATE XIII. EOCENE BLUFFS-GREEN R]YER . WYOMING . EOCENE TERTIAllY. ,389 there is no less than 2,000 feet of the series displayed, of which the whiteand brown paper shales occupy the upper 1,200 feet. Throughout thisthickness they are more or less intercalated with arenaceous beds, which atthe base of the shale-series rapidly increase in proportion and become moreand more calcareous, finally appearing either as marly sandstones or ascream3^-white, brittle, fine grained, earthy limestones. Capping the shales,and making the uppennost member of the series in the region of GreenRiver, are displayed about 100 feet of brown sandstone of massive fomis the heavy, dark-brown cap upon the bluffs in the region of GreenEiver City, where all traces of the original stratification are lost, and therock presents an apj^earance of somewhat peculiar local physical characteristics, especially the compactness, of this upp
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