Geology of the Florence Area, Wisconsin and Michigan
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Geology of the Florence Area, Wisconsin and Michigan GEOLOGICAL SURVEY PROFESSIONAL PAPER 633 Prepared under the auspices of U.S. Department of the Interior^ Geological Survey; University Extension The University of Wisconsin Geological and Natural History Survey; Michigan Department of Conservation^ Geological Survey Division Geology of the Florence Area, Wisconsin and Michigan By CARL E. DUTTON GEOLOGICAL SURVEY PROFESSIONAL PAPER 633 Prepared under the auspices of U. S. Department of the Interior) Geological Survey; University Extension The University of Wisconsin Geological and Natural History Survey; Michigan Department of Conservation, Geological Survey Division UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1971 UNITED STATES DEPARTMENT OF THE INTERIOR ROGERS C. B. MORTON, Secretary GEOLOGICAL SURVEY William T. Pecora, Director Library of Congress Catalog-card No. 77-610426 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 CONTENTS Page Page Abstract.--__-__-__--__-_--_______-________________ 1 Stratified rocks Continued Introduction, ______________________________________ 2 Middle Precambrian rocks Continued Location and surface features.___________________ 2 Paint River Group _______-__--__-_-----_- 26 Climate and vegetation,_______________________ 2 Dunn Creek Slate______________-__--_- 27 Accessibility_ _ ________________________________ 2 Definition and distribution.______-__- 27 Discovery and mining of iron ore_________________ 2 Description. ______________--------- 27 Previous geologic work__________________________ 4 Thickness and relations to adjacent fot%- Purpose and methods of this investigation.________ 5 mations_ _ ____-_---_-__-----_----- 29 Acknowledgments. __ _ ___________________________ 7 Conditions of deposition_-__--------- 30 General geology.___________________________________ 7 Age and correlation.________________ 30 Stratified rocks_____________________________________ 9 Riverton Iron-Formation._______________ 30 Lower Precambrian rocks._______________________ 9 Definition and distribution____-_____- 30 Quinnesec Formation._______________________ 9 Description. _-__-_--_-------------- 30 Description. ___________________________ 9 Thickness and relations to adjacent Amphibolite.. _ _____________________ 9 formations ______--_---_---------- 31 Schist.____________________________ 9 Conditions of deposition.____________ 32 Quartzite. _________________________ 10 Age and correlation.________________ 32 Felsic Metavolcanic rocks____________ 10 Post-Riverton strata___________---_----- 32 Thickness and relation to adjacent forma Distribution._ . __________----_---- 32 tions ________________________________ 11 Description. _________---_-----_---- 32 Character of original rock________________ 11 Conditions of deposition _____________ 33 Age and correlation______._______________ 11 Thickness and relations to adjacent Middle Precambrian rocks Animikie Series________ 11 formations. _ --------------------- 34 Baraga Group______________________________ 11 Age and correlation._______-__-__--- 34 Hemlock(?) Formation-_________________ 12 Cambrian (?) rocks. _ ---------------------------- 34 Michigamme Slate._____________________ 12 Intrusive rocks-________--___-----_----------------- 34 Definition, distribution, and lithology_ _ 12 Metagabbro._ ________--__---------------------- 34 Brule River block__________________ 13 Hoskin Lake Granite.___ ------------------------ 36 Keyes Lake block___________________ 14 Peavy Pond Complex.______------_------------- 37 Quartzite_ _____________________ 14 Structural geology.________-_---------_------------- 37 Strata younger than quartzite. 17 Brule River block __________----.-------------- 37 Pine River block.__________________ 18 Commonwealth syncline.___-____-.---------- 37 Slate, schist, and phyllite_ _______ 20 Other folds-.------------------------------ 38 Quartz graywacke-_____________ 20 Keyes Lake block-._________-__-___------------- 38 Amphibolite. __________________ 20 Pine River block_____--_------------------------ 39 Grunerite iron-formation ________ 21 39 Quartzitic conglomerate.________ 21 Popple River block-________-------_------------ Iron-formation. ________________ 22 Foliation and lineation ___________-_------__--- 40 Phyllite above quartzitic conglom Time of folding and faulting ____________------ 40 erate______________________ 23 Metamorphism. _________---_----------------------- 40 Greenstone agglomerate.________ 23 Chlorite zone._______--__--_-------------------- 40 Slate and metagraywacke_ _______ 23 Biotite zone.______-_--__----------------------- 40 Thickness and conditions of deposition. 23 Garnet zone _______-_------------------------ 41 Age and correlation.________________ 23 Staurolite zone_____._--_----------------------- 41 Badwater Greenstone__________________ 24 Graywacke-shale suite.________-------- --- 41 Definition, distribution, and general li- Iron-formation _ _________----------------- 42 thology._________________________ 24 Basic igneous rocks.____--__---------------- 42 Greenstone.. __ _ ____________________ 24 Sillimanite zone_______-__-_--------------------- 42 Amphibolite (metabasalt)____________ 25 Graywacke-shale suite _______--_---------- 42 Iron-formation_ _ __________________ 25 Basic igneous rocks ----------------------- 42 Slate, metaargillite, and quartz gray 43 wacke ___________________________ 26 Peavy node_____---_------_-------------------- Tuffaceous (?) rocks______________-__ 26 Time of metamorphism and relation to deformaticn_ 43 in IV CONTENTS Page Page Magnetic surveys._---------- 45 Economic geology Continued Ground magnetic survey 45 Iron-ore mines Continued Aeromagnetic survey. 46 Davidson mine____________. 48 Brule River block.. _. 46 Ernst mine.______________ 49 Keyes Lake block..__ 46 Explorations ____-__-__--______. 49 Pine River block___ 46 Nonmagnetic iron-formation. 49 Popple River block... 46 Welch_____.____. 49 Economic geology-______-__- 47 Polderman. ___________ 49 Iron-ore mines._______-. 47 Spread Eagle__ _ _______ 49 Florence mine. ____-. 47 Magnetitic iron-formation... 50 Badger mine. _______ 48 Guides to further exploration.... 51 Buckeye mine_-____- 48 References cited.__________________ 51 Commonwealth mine. 48 Index.___________________________ 53 ILLUSTRATIONS [Plates are In poc ket] PLATE 1. Map showing geology of Precambrian rocks in the Florence SE and Iron Mountain SW quadrangles, Florence County, Wis. 2. Map showing geology of Precambrian rocks in the Florence West and Florence East quadrangles, Florence County, Wis., and Iron County, Mich. 3. Geologic map showing lithology of the Riverton Iron-Formation and associated strata in Florence mine area, Florence County, Wis. 4. Generalized geologic map and sections showing major structural features of the Florence area, Wisconsin. 5. Generalized geologic map of Florence area, Wisconsin, and part of Michigan showing metamorphic zone". 6. Magnetic and geologic map of area near Keyes Lake, Florence County, Wis. 7. Aeromagnetic contour map of the Florence SE and Iron Mountain SW quadrangles, Florence County, Wis. 8. Aeromagnetic contour map of the Florence West and Florence East quadrangles, Florence County, Wis., and Iron County, Mich. Page FIGURE 1. Generalized geologic map of northern Wisconsin and northwestern Michigan..._________________________ 3 2. Geologic map showing lithology of the Michigamme Slate at the Little Commonwealth exploration. ________ 16 3. Map showing distribution and relation of the Michigamme Slate and Quinnesec Formation._______________ 19 4-12. Photographs: 4. Predominance of quartz pebbles in quartzitic conglomerate near the Pine River, Florence Cornty, Wis____________________________--__-_________.___________________ 21 5. Alinement of pebbles in quartzitic conglomerate.____________________________________________ 22 6. Ellipsoidal (pillow) structure in the Badwater Greenstone.____________________________________ 24 7. Pencil slate__----____________________________________________________...___________ 28 8. Graphitic slate breccia.___________________________________________________________________ 29 9. Chert breccia in Riverton or post-Riverton strata.___________________________________________ 34 10. Small sills of metagabbro in hornblende schist of the Quinnesec Formation._____________________ 35 11. Michigamme Slate.______________________________________________________________________ 43 12. Folded foliation in the Quinnesec Formation______________--__________________________.-_____ 44 TABLES Page TABLE 1. Lithologic sequence of Precambrian rocks in Iron and Dickinson Counties, Mich_________________________ 6 2. Rock units in the Florence area__________________________________________________________________ 8 3. Chemical analyses of specimens from the Dunn Creek Slate in Florence, Wis., area...-------------------- 28 4. Chemical analysis of interbedded siderite-chert from the Riverton Iron-Formation, Florence, Wis., area..___ 31 5. Chemical analysis of the Hiawatha Graywacke, Florence, Wis., area.___________________________________ 33 6. Chemical analyses and modes of three samples from the Michigamme Slate..____________________________ 43 7. Partial analyses of iron ores from Florence, Wis., area._____-_____---________-___----_-_-__-_-_--_---- 47 GEOLOGY OF THE FLORENCE AREA, WISCONSIN AND MICHIGAN By CARL E. DUTTON ABSTRACT The thickness of the formation may range from 2,000 to 15,000 feet. The Florence area, in northeastern Wisconsin and