Publisher's Synopsis
Excerpt from On the Quartz Keratophyre and Associated Rocks of the North Range of the Baraboo Bluffs
Irving in 1877 described the porphyry as occurring on the west side of the Baraboo River at the Lower Narrows. He considered the porphyry to be very distinctly bedded, with an east and west strike and a dip of 58° to 60° to the north. He also found that near the quartzite it changes to a distinct schist, which he thought to be allied to the greasy quartz schists at Devil's Lake. Farther west at the northern limit of the porphyry, he found the much fractured area. A schistose structure, which is apparent in places, was taken as bedding and as evidence of the clastic origin of the'rock. A specimen was analyzed and found to contain per cent. Of silica and a notably large quantity of soda as compared with potash.
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