—48— Aluminous minerals similar to those <strong>of</strong> the Lorrain Formation occpr in quartzites in the lower part <strong>of</strong> the Animikie "Series" = Marquette Range Supergroup (Church <strong>and</strong> Young, in press) <strong>of</strong> the south shore <strong>of</strong> Lake Superior (Keyes Lake quartzite, Sturgeon quartzite, Ajibik quartzite <strong>and</strong> Breakwater quartzite). Kaolinite is also present in the Baraboo <strong>and</strong> Barron quartzites <strong>of</strong> Wisconsin <strong>and</strong> pyrophyllite <strong>and</strong> diaspore were reported from the Sioux quartzite <strong>of</strong> <strong>Minnesota</strong> <strong>and</strong> South Dakota (Berg, 1931). Kyanite is present in the Medicine Peak Quartzite <strong>of</strong> S.E. Wyoming, the Petaca Schist <strong>of</strong> New Mexico <strong>and</strong> kaolinite, <strong>and</strong>alusite <strong>and</strong> diaspore have been found in the Hurwitz C quartzites <strong>of</strong> the Keewatin District <strong>of</strong> N.W.T. Bimodal size distribution in many <strong>of</strong> these quartzites may indicate that much <strong>of</strong> the clastic material was wind transported prior to sedimentation in an aqueous medium (Folk, 1968). Similar aluminous quartzites <strong>of</strong> similar age from other continents include those <strong>of</strong> Finl<strong>and</strong> (Jatulian quartzites), Brazil (Jacobina Series), India (Iron Ore Series) <strong>and</strong> South Africa (Witwatersr<strong>and</strong> System). Some <strong>of</strong> these extremely widespread quartzites may be deposits formed as a result <strong>of</strong> post-glacial transgression. If the formation <strong>of</strong> kaolinite in the quartzites took place under climatic conditions similar to those unde,r which present day bauxites <strong>and</strong> laterites are formed, there must have been a significant amelioration <strong>of</strong> climate following deposition <strong>of</strong> the Cowg<strong>and</strong>a Formation <strong>and</strong> its possible correlatives. REF ERENCES Berg, B. L. 1937. An occurrence <strong>of</strong> diaspore in quartzite. Amer. Mineralogists .v. 22, pp. 997—999. Church, W. R. 1967. The occurrence <strong>of</strong> kyanite, <strong>and</strong>alusite <strong>and</strong> kaolinite in Lower Proterozoic (Ruronian) rocks <strong>of</strong> Odtario (abst.) Tech. Prog. Geol. Assoc. Can. Meet. Kingston, Ontario, pp. 14-15. Church, W. ft. <strong>and</strong> Young, C. M. (in press). Discussion <strong>of</strong> the Progress report <strong>of</strong> the Federal-Provincial Committee on Huronian stratigraphy. Can. J. Earth Sc. v. 7. Folk, R. L. 1968. Bimodal süpermature s<strong>and</strong>stones: product <strong>of</strong> the desert flc,or. XXIII International Geological Congress Section 8; Genesis <strong>and</strong> Classification <strong>of</strong> Sedimentary Rocks. pp. 9-32. Logan, W. B. <strong>and</strong> Sterry Hunt, T. 1855. H. Bossange et fils, Paris. 100 pp. Esquisse geologique du Canada. Murray, Alex<strong>and</strong>er. 1849. On the north coast <strong>of</strong> Lake Huron. Geol. Surv. Canada, Rept. Prog. pp. 93-124. Ojakangas, R. W. 1965. Petrography arid sedimentation <strong>of</strong> the Precambrian Jatulian quartzites<strong>of</strong> Finl<strong>and</strong>. Bull. Comm. Geol. Finl<strong>and</strong>e. No. 214, 74 pp. Young, G. M. (in press). An extensive Early Proterozoie glaciation in North America? Palaeogeog. Palaeoclimat. Palaeoecol.
—49— PROTEROZOIC ROCKS IN THE THUNDER BAY AREA May 9, 1970 Prepared by. J. M. Franklin, Lakehead <strong>University</strong>, Thunder Bay CR. Kustra, Ontario Department <strong>of</strong> Mines, Thunder Bay