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III. On the Laurenation Formation: its Mineral, Constitution, its Geographical Distribution, and its Residuary Elements of Life
Published online by Cambridge University Press: 01 May 2009
Extract
It is indended in this paper to present a general outline of the Laurentian Formation under the heads mentioned in the above title; dwelling principally on the latter clause, its residuary elements of life, or, in other words, on those mineral substances, contained within it, which at some earlier period have been the constituents of organic bodies. This formation, or system of rocks, which have been called ‘fundamental,’ has of late years very generally received the name of ‘Laurentian,’ a geographical denomination, taken from the country (Laurentide or Laurentian Mountains) in which it has been well studied, and where it exists in vast force. An assemblage of metamorhosed rocks may usually br considered ‘Laurentain,’ when over great spaces (with or without the intervention of the Huronian and Cambrian rocks) it underlies discordantly beds more or less fossiliferous, named ‘Primordial’ in Bohemia, ‘Lingula-flags’ in Wales, ‘Potsdam Sandstone’ in North America.
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References
page 155 note * See Geol. Report Canada, 1863, p. 50;Google Scholar and Quart. Journ. Geol. Soc., vol. xix. p. 36.Google Scholar
page 155 note † See the successive Reports on the Geology of Canada, by Sir Logan, W. E. and his colleagues, especially the large comprehensive Report for 1863, as well as the Descriptive Catalogue of Canadian Minerals and Rock, Internat. Exhib. 1862.Google Scholar
page 155 note ‡ Report, 1863, p. 22. These varying triclinic felspars being anorthic in crystalization and approaching anorthite in composition, Delesse proposed to give them the name ‘anorthose’, and ‘anorthosite’ to the rock-masses formed of them.Google Scholar
page 155 note § By ‘gneiss’ is meant a rock consisting of the same materials as granite (with or without hornblende), but with a lamellar structure.
page 156 note * In 1846 Elie de Beaumont announced the sedimentary nature of the Swedish gneiss; Bullet. Soc. Géol. France, n.s. vol. iv. p. 501.Google Scholar
page 157 note * Geol. Report, 1854, pp. 374, 383.Google Scholar
page 157 note † Report, 1863, p 37.Google Scholar
page 157 note ‡ Compare Rogers's Final Rep. Geol. Pennsylvania, vol. i. p. 62; ii. pp. 744, 747, &c.Google Scholar