. 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 . ESCARPMENT AND TALUS OF SLATE. lull. Many of them occur on the shores of this lake, like the one represented in thepreceding sketch. ON THE NORTHWEST SHORE OF LAKE SUPERIOR. 415Another example of a slate escarpment, with its talus, is exhibted in this The long point below the mouth of Arrow River is composed of a fine-grainedhornblendic rock, with a slaty structure. It splits into thin layers, and is
. 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 . ESCARPMENT AND TALUS OF SLATE. lull. Many of them occur on the shores of this lake, like the one represented in thepreceding sketch. ON THE NORTHWEST SHORE OF LAKE SUPERIOR. 415Another example of a slate escarpment, with its talus, is exhibted in this The long point below the mouth of Arrow River is composed of a fine-grainedhornblendic rock, with a slaty structure. It splits into thin layers, and is regularlyjointed. On the gentle slope to the lake, where it is bare, it presents the appear-ance of a tessellated pavement. At the west end of the lake is a ridge four hundredand fifty-nine feet in height, the lower part of which is composed of argillaceousslate (No. 25). It dips southeast, into the side of the ridge, at a high angle. Eastof the slate-beds is a high ridge of syenite (No. 26), which extends to the marginof the lake, and forms mural precipices on the hillside. The upper part of theridge, and near the hill over which the portage to Wisacode River passes, the rockbecomes fine-grained, and is jointed (No. 28). The succeeding ridge, which comesto the lake opposite the point above the mouth of Arrow River, is finer-grained andpresents a slaty structure. It resembles slaty greenstone (No. 29). The following-section illustrates
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Keywords: ., booksubjectbotany, booksubjectgeology, booksubjectpaleontology
