I. The Anorthosytes of the Minnesota Coast of Lake Superior, And, II. The Laccolitic Sills of the North-West Coast of Lake Superior

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Excerpt from I. The Anorthosytes of the Minnesota Coast of Lake Superior, And, II. The Laccolitic Sills of the North-West Coast of Lake Superior: With a Prefatory Note One the Norian of the NorthwestThe third annual report of the director of the United States geological survey contains a somewhat later (1883) exposition of the Keweenawan by Prof. Irving, embracing some new field observations and some new lithological studies. Here he still retains the gabbro series, whether in Wisconsin or in Minne sota, in the Keweenawan, announces a new variety of the gab bro series from Minnesota, viz anorthite rock. Which he says is merely a coarse gabbro, in which all the ingredients but the feldspar are wanting, (p. 97) and gives some of the de tails of an unconformity of the gabbro series below the diabases of the rest of the formation, in the Bad river region. This passage is so important that it is worth quoting in full.About the PublisherForgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.comThis book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully, any imperfections that remain are intentionally left to preserve the state of such historical works.