. Report of a geological survey of Wisconsin, Iowa, and Minnesota : and incidentally of a portion of Nebraska Territory : made under instructions from the United States Treasury Department . b a b c b a. Greenstone. J, b, b. Metamorphosed beds. c. Clay and marl. The rocks clip east and west, and on the east side the dip amounts to 41°. Inthe same bay, however, two hundred yards below the dike, the dip is to the west,at an angle of 9°. This continues for about three hundred yards, when the dipgradually changes until it is to the east. The dike producing the disturbances inthe bedded rocks is no
. Report of a geological survey of Wisconsin, Iowa, and Minnesota : and incidentally of a portion of Nebraska Territory : made under instructions from the United States Treasury Department . b a b c b a. Greenstone. J, b, b. Metamorphosed beds. c. Clay and marl. The rocks clip east and west, and on the east side the dip amounts to 41°. Inthe same bay, however, two hundred yards below the dike, the dip is to the west,at an angle of 9°. This continues for about three hundred yards, when the dipgradually changes until it is to the east. The dike producing the disturbances inthe bedded rocks is not visible for some distance on the shore, but in the secondbay below the island it is again seen (No. 333) above the water-level, overlaid byabout sixty feet of metamorphosed rocks. In the bottom of this bay the north-45°-east dike (No. 613) contains immense fragments of a massive felspar rock* (). At the projecting point below this, there are some beds of trap betweenthose of the metamorphosed rocks, which appear to be lateral injections from thedike. At one point the section consists, as here shown, in descending order, of, a. Trap-beds. b. c c. Red clay and marl. a a. Trap-beds. 1st, a bed of red clay and marl, overlying a bed of basaltic rock; 2d, thinly lami-nated siliceous shale (No. 316), very much altered in some places, and nearly un-altered in others. It contains organic impressions like those found on PassabikaRiver, and also large waterworn fragments of other rocks. It weathers into A bed of basaltic rock, which has altered the shales near its contact with theminto a hard, compact rock, with a hackly fracture, and a semi-columnar structure. * An analysis of this rock is given elsewhere. 358 DESCRIPTION OF THE COUNTRY The same rocks continue through the next bay, the lower beds being amygda-loidal, and filled with zeolites. At the point below, and immediately after turningit, the beds are thin, and tilted up, as seen in the figure be
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