. The copper-bearing rocks of lake Superior / by Roland Duer Irving. Geology; Geology; Copper ores; Copper ores. 142 COPPEE-BBAEING ROCKS OF LAKE SUPEEIOE. From Grand Marais westward to Poplar Eiver the trend of the strata is more easterly than that of the coast, so that in looking in that direction these hill blocks are seen succeeding each other in such a way as to have suggested the very apposite epithet of "Saw Teeth ; An attempt to represent this appearance is made in the accompanying outline Fig. 1.âOutlines of coast hills for 20 miles above Grand Marais, Min
. The copper-bearing rocks of lake Superior / by Roland Duer Irving. Geology; Geology; Copper ores; Copper ores. 142 COPPEE-BBAEING ROCKS OF LAKE SUPEEIOE. From Grand Marais westward to Poplar Eiver the trend of the strata is more easterly than that of the coast, so that in looking in that direction these hill blocks are seen succeeding each other in such a way as to have suggested the very apposite epithet of "Saw Teeth ; An attempt to represent this appearance is made in the accompanying outline Fig. 1.âOutlines of coast hills for 20 miles above Grand Marais, Minn. In the woods of the North Shore away from the lake, the same feature is constantly repeated; ridges are everywhere met with trending with the strike of the formation, sloping gradually to the southeast, and dropping off abruptly to the northwest. This structure has been attributed by N. H. WinchelP to faulting, each drop being regarded as the result of a fault. There may be a few such faults, but it is evident enough that the case is just such as is found in every region of flat-dipping hard rocks, and espe- cially where softer layers are interleaved, as in this case. On the south shore of the lake the dip is commonly higher, and although the same structure occurs the front slope is often flatter than the dip slope. In the eastern part of Keweenaw Point, where the dip flattens, the structure comes out finely in a series of bold ridges. Towards Portage Lake, however, the dip becomes as high as 50° or more, and the several ridges merge into one broad swell. This holds until the Porcupine Mount- ains are reached, where, though the dip-angle is as high as 30°, the struct- ure is most beautifully illustrated in the outer ridge. This ridge rises â i-Eeport of the Geological Survey of Minnesota for 1878, p. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illu
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectgeology, bookyear1883
