. Annual Reports of the Department of the Interior for the Fiscal Year Ended June 30, 1900--Twenty-First Annual Report of the United States Geological Society. ARCHKAN Including considerable Including consiareas of Algonkian franite areasofArcli (the iron-bearin( I tes GEOLOGK^AL ^L\P OF (^ SHOWING PRCompiled from (MByial maps S S i TWENTY-FIRST ANNUAL REPORT PART III pl. X LVlll. !l« LAKE SrPERIOK REGIOX *IHIAM HOCKS jp e. ai\dC&nadiai) Sur\ei-s I* A Ahl Original Homnian Ah Z Manpusftp iron ^t^iartn^ .wrt*r Ah3 Crystal Falls uwi -hearing»tri(» Ah 4 Sdmtmunrr iron braru%g xenAs- h5 Wisti
. Annual Reports of the Department of the Interior for the Fiscal Year Ended June 30, 1900--Twenty-First Annual Report of the United States Geological Society. ARCHKAN Including considerable Including consiareas of Algonkian franite areasofArcli (the iron-bearin( I tes GEOLOGK^AL ^L\P OF (^ SHOWING PRCompiled from (MByial maps S S i TWENTY-FIRST ANNUAL REPORT PART III pl. X LVlll. !l« LAKE SrPERIOK REGIOX *IHIAM HOCKS jp e. ai\dC&nadiai) Sur\ei-s I* A Ahl Original Homnian Ah Z Manpusftp iron ^t^iartn^ .wrt*r Ah3 Crystal Falls uwi -hearing»tri(» Ah 4 Sdmtmunrr iron braru%g xenAs- h5 Wistionstn Ia/Uv veri^ h6 Pmokfe-Goqrbic irtyrtOtmnng J h7 Blaticffnr/uori hfoTUitf XrAiSt AhM VerntHit <»i firtuint/A-r^^tfAhl3 /))M^<y .v<Vi(.y/.« orca/nu/n . VAN TIME AND DEPTH OF CONCENTRATION. 881 process of development of the ores at this horizon antedated Ke\veena-wan time. While, therefore, it is plain that the })eginning- of coiutMi-tration of the ores must be placed shortly after the different iron-bearing-formations were deposited, if the theory advanced on the previouspages be correct, it is clear that the beginning of the final and mostimportant enrichment of the ore deposits occurred in Algonkian , in those districts in which great masses of Keweenawanrocks were laid down upon the Huronian rocks this process could nothave begun unti
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Keywords: ., bookauthorunitedst, bookcentury1900, bookdecade1900, bookyear1901
