. The copper-bearing rocks of lake Superior / by Roland Duer Irving. Geology; Geology; Copper ores; Copper ores. 204 COPPEE-BEAEING EOCKS OF LAKE SUPEEIOE. weenaw Point Range is one of the greatest interest. A moment's inspection of the map of Plate I will serve to show that towards the east the two ranges are widely separated, the distance between them, even west of the Ontonagon, being as much as 18 miles, while still further west they rap-. Rg. 3.—Map of Exposures in Vicinity of 'West Brancli of Ontonagon Eiver, T. 46. E. 41 W., Michigan. idly approach, and finally join. The beds of both ra
. The copper-bearing rocks of lake Superior / by Roland Duer Irving. Geology; Geology; Copper ores; Copper ores. 204 COPPEE-BEAEING EOCKS OF LAKE SUPEEIOE. weenaw Point Range is one of the greatest interest. A moment's inspection of the map of Plate I will serve to show that towards the east the two ranges are widely separated, the distance between them, even west of the Ontonagon, being as much as 18 miles, while still further west they rap-. Rg. 3.—Map of Exposures in Vicinity of 'West Brancli of Ontonagon Eiver, T. 46. E. 41 W., Michigan. idly approach, and finally join. The beds of both ranges dip northward. Should we suppose a continuous series beneath the intervening horizontal sandstone, we should obtain an incredible thickness, and one which west- ward must diminish with an incredible rapidity, for after the two ranges have joined the total apparent thickness of the Lower Division of the series does not exceed 33,000 feet, or only 8,000 feet more than on Keweenaw Point. That there is a fold beneath the sandstone-filled area seems im- probable. There is no sign of a southern dip along the south side of the Keweenaw Range during all its course from Bgte Grise Bay to its junction with the South Range. I had at one time the idea that such a fold might exist,^ Foster and Whitney in their report indicating the existence of a ^See Geology of Wisconsin, Vol. Ill, Part I, p. 19, Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Irving, Roland Duer, 1847-1888. Washington, Govt. Print. Off.
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