Synopsis
This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1888 Excerpt: ... original surface indicated by the folds are now almost wholly planed off and the sandstone lies upon a relatively level surface. Several sections and views illustrative of the contacts of the sandstone with the two adjacent formations are presented herewith. The Potedam-Huronian unconformity of the north shore of Lake Huron.--At Marquette, on the Michigan shore of Lake Superior, the outcrop line of the Potsdam sandstone divides. To the west the sandstone skirts the shore as far as Keweenaw Bay, having immediately behind it a more elevated region, occupied by the higher portions of the ancient basement. To the east of Marquette it forms the shore line all the way to the eastern end of the lake, the older rocks being in this distance wholly concealed by the sandstone formation or by the waters of Lake Superior. The eastern termination of the lake is at the Sault Ste. Marie. A few miles north and again east from this point, however, the basement formations rise again from beneath the sandstone, forming most of the eastern side of Lake Superior and of the northern shore of Lake Huron (PI. XL). Fia. 88. Section through Campement d'Ours Island and the northern end of St. Joseph Island, north shore of Lake Huron, looking east. The inclined layers are quartzites and conglomerates of the Huronian; the horizontal layers are the Potsdam and Calciferous below and Trenton above. After Logan. Along the shore of the north channel of the latter lake, between the St. Mary's and Thessalon Rivers, and for an unknown distance farther eastward, is the series to which the name of Huronian was originally given by Logan and Murray. Everything about this series, as I have argued elsewhere, goes to indicate its identity with the ironbearing formation of the Marquette region and wit...
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