Definitions

from Wiktionary, Creative Commons Attribution/Share-Alike License

  • proper n. The younger division of the Proterozoic eon as represented by rocks in the Great Lakes region of the United States

Etymologies

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Examples

  • Keweenawan rocks to the group of limestones so widespread over the North American continent and so full of fossils, which to older geologists and oil drillers have been known, in a broad way, as Trenton.

    Popular Science Monthly Oct, Nov, Dec, 1915 — Volume 86

  • A similar cycle may be traced from the Keweenawan rocks to the group of limestones so widespread over the North American continent and so full of fossils, which to older geologists and oil drillers have been known, in a broad way, as Trenton.

    The Scientific Monthly, October-December 1915

  • One of the interesting features of the concentration of Lake Superior iron ores is the fact that it took place long ago in the Keweenawan period, preceding the deposition of the flat-lying Cambrian formations, at a time when the topography was mountainous and the climate was arid or semi-arid.

    The Economic Aspect of Geology

  • Here again it was at first supposed that the enrichment was related to the present erosion surface; but upon further studies the fact was disclosed that the concentration of the ores took place in the period between the deposition of Keweenawan and Cambrian rocks, and thus a new light was thrown on the possibilities as to depth and distribution of the ores.

    The Economic Aspect of Geology

  • After the Keweenawan was uplifted to form land, percolating waters leached out much of the copper diffused in the lava sheets and deposited it within steam blebs as amygdules of native copper, in cracks and fissures, and especially as a cement, or matrix, in the interbedded gravels which formed the chief aquifers of the region.

    The Elements of Geology

  • In the igneous rocks copper, next to iron, is the most common of all the useful metals, and it was especially abundant in the Keweenawan lavas.

    The Elements of Geology

  • Huronian more than two miles thick, while the Keweenawan exceeds nine miles in thickness.

    The Elements of Geology

  • Keweenawan is composed of immense piles of lava, such as those of

    The Elements of Geology

  • The researchers found that the composition of magnetic isotopes in rocks taken from Antarctica's Coats Land were "indistinguishable from rocks of the Keweenawan province" in Michigan.

    NPR Topics: News

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