A Geological Section from Bessemer Down Black River
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1907 edition. Excerpt: ...faulting in the river in Sec. 29, T. 49 N., and, indeed, it is probable that all these indications are of the same jfault. The dip of the fault' plane in all the cases is toward the east0 at a high angle. xxxiii. (82). Unexposed: --Tliis is the widest unexposed area in the whole cross section. It represents at a dip of 64 a rock thickness of about 8,500 feet. It is possible that there is a strike fault in this gap representing the continuation of the great fault that bounds the south side of the Keweenawan on Keweenaw Point, and, if so, this calculated thickness of 8,500 feet would be incorrect. The rocks above the space are basic, as are also the rocks below, and it is probable that the under._ lying rocks0are also basic.. Division IX. The Porphg/rites. This division is a rather mixed division, because in it are melaphyres, both ophitic and non.ophitic, felsites, porphyrites which closely approach Irving's quartzless porphyries, and labradorite porphyrites, but of all these the last are the most conspicuous. This division might be called one in which are conspicuous labradorite porphyrites. There are labradorite porphyrites outside this division but they are not such that their nature is revealed at a glance like these. Besides the fact that in this part these rocks are conspicuous the division is also marked by the gabbro at its base. This division shows the greatest variety in the kind of rocks that build it up of all the divisions of the column. It covers practically the north of the two Bessemer Ridges. All of the outcrops are shown in the hills which are so characteristic of the base of the Keweenawan about here. The most northerly exposures of the division are seen in Powder Mill Creek. i. (83). This is a blue colored..
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- 13 Sep 2013
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