. 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 . appearance at the contact. A portionof the bed near the gutter has the appearance of jasper. (No. 87.) The directionof the gutter is from north to south. The first high ridge is about a mile and ahalf north of the lake-shore. A short distance further on, is an exposure of siliceous shale (No. 90), overlaidby altered sandstone (No. 89) ; both rocks dipping southwest at an angle of Vl°.Just above the long po
. 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 . appearance at the contact. A portionof the bed near the gutter has the appearance of jasper. (No. 87.) The directionof the gutter is from north to south. The first high ridge is about a mile and ahalf north of the lake-shore. A short distance further on, is an exposure of siliceous shale (No. 90), overlaidby altered sandstone (No. 89) ; both rocks dipping southwest at an angle of Vl°.Just above the long point below the mouth of Manitobimitagico River, and near themouth of a small stream which comes in there, are some low exposures of No. the point itself, the trap overlies a breccia, from eight to ten feet in thickness,and filled with zeolites. These rocks continue to form the shore as far as the mouthof Manitobimitagico River, a short distance above which a trap ridge strikes the 302 DESCRIPTION OF THE COUNTRY BORDERING: lake. On the northwest side of the ridge, this rock (No. 92), presents beautifulclusters of columns, as shown in the subjoined sketch by Major Owen. They are. CLUSTERS OF INCLINED COLUMNAR BASALT, LAKE SUPERIOR. mostly pentangular, and from ten to eighteen inches in diameter. The sedimentaryrocks near the trap dip 30° to the northwest, and the columns make about the sameangle with the horizon, favouring the idea that the basaltic rock is not a dike, buta bed. At another point, the columns stand without order or regularity in referenceto the bedded rocks, and are separated from them by four feet of breccia, as shownin the annexed cut, and such as is found to underlie the basaltic beds of other
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