Water Supply and Irrigation Papers of the United States Geological Survey . creeping features have been noted in sec. 33, T. 100 N., R. 59 W., ona slope above the Dakota sandstone and below the level of the chalk-stone. It is impossible to estimate the thickness of the formationwith any accuracy, but there is clear evidence that the clayey membercorresponding to the Benton is found here in considerable is probably 50 feet thick. Elsewhere it has been reported in bor-ings as underlying the chalkstone and lying on the sandstones of theDakota. Before the deposition of t
Water Supply and Irrigation Papers of the United States Geological Survey . creeping features have been noted in sec. 33, T. 100 N., R. 59 W., ona slope above the Dakota sandstone and below the level of the chalk-stone. It is impossible to estimate the thickness of the formationwith any accuracy, but there is clear evidence that the clayey membercorresponding to the Benton is found here in considerable is probably 50 feet thick. Elsewhere it has been reported in bor-ings as underlying the chalkstone and lying on the sandstones of theDakota. Before the deposition of the Colorado formation the Dakota sand-stone seems to have been somewhat eroded, especially in the highestportions adjoining the quartzite. Possibly this was due to contempo-raneous erosion rather than to true unconformity; that is, it was dueto the action of tidal currents or waves cutting out channels withoutany exposure to the action of streams upon a land surface. Moreover,the Colorado overlaps considerably beyond the edge of the Dakotasandstone. SURVEY. 90 m;T chin sew co. R-57 w | W I + 210 (etc.)Representative wells and their depth in feetwhich obtain pump water at base of till MAP OF A PORTION OF Ej Showing depths to w; BY S(! L ...... J L 1 0 0 -50 50 -100 100 - 150 WATER-SUPPLY PAPER N° 34
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