DOCSLIB.ORG

Illite/Smectite Geothermometry of the Proterozoic Oronto Group, Midcontinent Rift System

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Illite/Smectite Geothermometry of the Proterozoic Oronto Group, Midcontinent Rift System Clays and Clay Minerals. Vol. 41 , No. 2, 134-147, 1993. ILLITE/SMECTITE GEOTHERMOMETRY OF THE PROTEROZOIC ORONTO GROUP, MIDCONTINENT RIFT SYSTEM KIRSTEN L. PRICE AND S. DOUGLAS McDOWELL Department of Geological Engineering, Geology and Geophysics, Michigan Technological University 1400 Townsend Drive, Houghton, Michigan 49931 Abstract-Characterization of the Nonesuch Formation, middle unit of the Proterozoic Oronto Group, as a potential hydrocarbon source for the Lake Superior basin portion of the Midcontinent Rift system requires an understanding of the thermal maturity of the region and its relationship to the thermal history. Illitelsmectite (liS) expandability data were collected from the Nonesuch Formation and the overlying Freda Sandstone and compared with organic thermal maturity data; both data sets coupled with a thermal and burial history for the White Pine area ofMichigan allow regional interpretation of maximum formation temperatures of the Nonesuch Formation and the Freda Sandstone with respect to time. Samples collected from drill holes in northeastern Wisconsin display nearly pure smectite within the lower Freda Sandstone trending abruptly to ordered liS within the Nonesuch Formation. Regular trends of decreasing expand­ ability with depth occur in four other drill holes to the northeast. Comparison ofI/S expandability between similar stratigraphic intervals reveals a significant trend of increasing thermal maturity to the northeast, with the lowest thermal maturities observed in the Iron River Syncline area just west of White Pine, Michigan. IISgeothermometry suggests maximum temperatures in the Nonesuch Formation of 1400c in Wis­ consin, 1150C in the Iron River Syncline area, 160·C at White Pine, and 1900c near the southern portions of the Keweenaw Copper District. The geographic pattern of temperatures determined from li S geother­ mometry is identical to that determined from organic thermal maturity indicators in the Nonesuch Formation (Imbus et al., 1988, 1990; Hieshima and Pratt, 1991; Pratt et al., 1991; Mauk and Hieshima, 1992). Regular variations in liS expandability with depth occur in the Freda Sandstone and the Nonesuch Formation near the southern limits of the Keweenaw Copper District. These variations suggest a fossil geothermal gradient of 550C/ km and limit the thickness of sediment above the Nonesuch Formation to approximately 3 km. In comparison, 3.6 km of Freda Sandstone are presently exposed near the Wisconsin border, and numerical modeling suggests a range of 4-6 km of sediment overlying the Nonesuch For­ mation. None of the data indicate the presence of the Bayfield Group sediments above the Nonesuch Formation at the time of clay diagenesis. Samples from White Pine suggest a two-stage burial history: I) clay reaction, possible hydrocarbon maturation, and copper-sulfide mineralization at maximum temper­ atures above 100·C during the main rifting and burial event, followed by 2) fracturing, reverse faulting, and fluid circulation during a rift-terminating compressional event that may have allowed petroleum migration and native copper mineralization at temperatures below 100·C. Abrupt changes in liS ex­ pandability with depth and the presence of poorly crystalline liS (greater than 80% expandable) and kaolinite in the Freda Sandstone in Wisconsin appear to represent later overprinting of the diagenetic assemblage by fluids that were probably cooler and of differing composition than earlier diagenetic fluids. However, the authigenic assemblage from the vicinity of White Pine, Michigan, which includes up to 25% expandable liS, appears to represent a diagenetic profile formed during the main rifting and burial event. Therefore, these expandable liS-type clays are essentially 1.0 billion years old. Key Words-Diagenesis, IllitelSmectite, Mineralization, Proterozoic, Retrograde, Thermal history. cial to the evaluation of its potential as a hydrocarbon INTRODUCTION source rock. Hydrocarbon exploration in the Midcontinent Rift The great age of the Nonesuch Formation and the system of North America (Figure I) has to date yielded other units of the Upper Keweenawan Oronto Group no economic reserves of either oil or gas (Dickas, 1986). significantly reduces the availability and reliability of However, speculation regarding its potential as a fron­ traditional methods of assessing the thermal maturity tier oil province continues. The Nonesuch Formation and thus the thermal history of sediments. To over­ hosts the large stratiform copper-sulfide deposit at White come this problem, illite/smectite (I/S) expandability Pine, Michigan. Mature oil seeps occur locally within (%Exp) data were used as a thermal maturity indicator the mine raising the possibility that the Nonesuch For­ (e.g., Waples, 1980; Pollastro and Barker, 1986; Pol­ mation may provide an economic hydrocarbon source lastro, 1990) and compared with available organic within the Lake Superior region. Understanding the thermal maturity data. These results were coupled with thermal evolution of the Nonesuch Formation is cru- a calculated thermal and burial history model for White Copyright © 1993, The Clay Minerals Society 134 Vol. 41 , No. 2, 1993 liS geothermometry of the I. I-Ga Oronto Group 135 JacOb,,,1I11 S5 ... Bayfl.ld Oroup N LAKE SUPER IOR Sindstoni r ~ Coppa, "I,bor CDntllomlral1 ~ Por tlg. l8ka Volcanic. Figure I. Geologic map of the Lake Superior region of the Midcontinent Rift system (inset) and the corresponding stratigraphy. 00-5, DO-14, WPB-I, WP, and W-II refer to collar location of drill holes from which samples were taken for this study. The Presque Isle Syncline is located about 25 km west-southwest of White Pine, Michigan; drill hole WPB-I is located on the southern limb of the Iron River Syncline. Modified from Daniels (1982), Green (1983) and Imbus et at. (1988). Pine, Michigan (Price et aI., in prep.) to estimate max­ oldest unit of the Oronto Group, the Copper Harbor imum formation temperatures for the Nonesuch For­ Conglomerate, interfingers with the overlying None­ mation with respect to time. There are two primary such Formation and includes lava flows known as the objectives of this project: 1) assessment of the thermal Lake Shore Traps. A high-precision U-Pb date ofl094.1 maturity of the Oronto Group with respect to depth ± 3.6 Ma for the Lake Shore Traps provides the age and geographic location using IIS geothermometry, and of deposition for the middle Copper Harbor Conglom­ 2) comparison of IIS expandability values to organic erate (Davis and Paces, 1990). The Nonesuch For­ thermal maturity indicators with respect to local and mation and the Freda Sandstone exhibit a conformable regional geologic events to assess the utility of IIS ex­ and gradational contact frequently extending over sev­ pandability as a thermal maturity indicator in ancient eral meters (Daniels, 1982). sedimentary basins. To avoid complications resulting from comparison of different lithologies, the study excluded the Copper Geologic setting Harbor Conglomerate and focused on the Nonesuch The Keweenawan stratigraphy (Figure 1) of the Lake Formation and the Freda Sandstone. The Nonesuch Superior portion of the Midcontinent Rift system rep­ Formation consists primarily of gray to black mica­ resents a classic rift sequence consisting of 3 to 5 km ceous siltstone and shale lithologies. Rock fragments of Portage Lake Volcanics overlain by a minimum of and quartz dominate the detrital component. Lithic 6 km ofOronto Group rift sediments. The Keweenaw­ fragments include primarily mafic volcanic fragments, an section of the region also includes the Bayfield Group although silicic and intermediate volcanic fragments of northern Wisconsin and the Jacobsville Sandstone have also been identified (Hite, 1968). Twenty to SO of Upper Michigan. The relationship between the percent of the detrital component is composed of vol­ Oronto Group, the Bayfield Group and the Jacobsville canic rock fragments, while undulatory quartz, plagio­ Sandstone remains unclear, although Bayfield Group clase, potassium feldspars and opaque minerals com­ equivalents may rest unconformably on the Oronto prise the remaining SO to 80 percent. The most common Group units offshore beneath Lake Superior (Cannon cement is calcite, although silica, laumontite, and he­ et al., 1989). Exposures of the Portage Lake Volcanics matite also frequently occur (Hite, 1968). Matrix clays, and the Oronto Group occur along the Lake Superior primarily chlorite and illite (which probably includes shoreline from the Keweenaw Peninsula of Upper liS), average about 5.3% of the rock volume (Hite, Michigan, southwest into Wisconsin (Figure 1). The 1968; Vogel et al., 1976) and probably formed from 136 Price and McDowell Clays and Clay Minerals ations in compositional maturity are marked by fluc­ tuations in the relative percentages of quartz and vol­ canic fragments (Hubbard, 1975). Silicic and I intermediate volcanic fragments dominate mafic frag­ ments, while other common framework minerals in­ ~I clude potassium feldspars, plagioclase, and undiffer­ entiated opaque minerals (Hite, 1968). As in the ~Io . Nonesuch Formation, cements include calcite, quartz, ~I laumontite, hematite, and occasionally chlorite (Hite, 1968). Clay minerals dominate the matrix, comprising ~ about 7.8% of the rock volume (Hite, 1968). Prelim­ inary XRD studies of the Freda Sandstone indicate ~ that the clay composition, chlorite, illite, and liS are I very similar to that of the Nonesuch Formation (Price and McDowell, 1991).
Load more

Recommended publications
  • A Field and Petrographic Study of the Freda
    A FIELD AND PETROGRAPHIC STUDY OF THE FREDA FORMATION ALONG THE MONTREAL RIVER, GOGEBIC COUNTY, MICHIGAN fey GORDON R. SMALE A THESIS Submitted in partial fulfillment of the requirements for the degree of Master of Science in Michigan State University East Lansing, Michigan 1958 ProQuest Number: 10008738 All rights reserved INFORMATION TO ALL USERS The quality of this reproduction is dependent upon the quality of the copy submitted. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if material had to be removed, a note will indicate the deletion. uest. ProQuest 10008738 Published by ProQuest LLC (2016). Copyright of the Dissertation is held by the Author. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code Microform Edition © ProQuest LLC. ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106- 1346 A FIELD AND PETROGRAPHIC STUDY OF THE FREDA FORMATION ALONG THE MONTREAL RIVER, GOGEBIC COUNTY, MICHIGAN •"by Gordon R „ Smal'e ABSTRACT The Montreal River provides a geographic boundary between Wisconsin and Michigan on the south shore of Lake Superior. A geologic study, both field and laboratory, was made of the 12,000 foot thickness of steeply dipping Freda for­ mation exposed along this river. The field study Includes mapping of sedimentary structures In an effort to determine the dominant current directions during deposition of the formation. Pebble and quartz grain orientation as well as heavy mineral and rock composition analyses were made In the laboratory to supplement the field work.
    [Show full text]
  • G-012011-1E Geological Precambrian Timeline Midwest
    Copper Harbor Conglomerate Gunflint Formation: Breccia with white quartz Precambrian Geologic Events in the Mid-Continent of North America G-012011-1E 1 inch (Century Mine, Upper Peninsula MI) (Sibley Peninsula, Thunder Bay, ON) Compiled by: Steven D.J. Baumann, Alexandra B. Cory, Micaela M. Krol, Elisa J. Piispa Updated March 2013 Oldest known rock showing a dipole magnetic field: red dacite in Austrailia Paleomagnetic Line 3,800 3,700 3,600 3,500 3,400 3,300 3,200 3,100 3,000 2,900 2,800 2,700 2,600 2,500 2,400 2,300 2,200 2,100 2,000 1,900 1,800 1,700 1,600 1,500 1,400 1,300 1,200 1,100 1,000 900 800 700 600 500 Paleozoic Period Siderian Rhyacian Orosirian Statherian Calymmian Ectasian Stenian Tonian Cryogenian Ediacaran Eoarchean Paleoarchean Mesoarchean Neoarchean Era Paleoproterozoic Mesoproterozoic Neoproterozoic Eon Archean Proterozoic Pass Lake Kama Hill Sibley Group Sediments (Sibley Basin, Thunder Bay Area, ON) McGrath Gneiss McGrath Complex (EC MN) Metamorphic and cataclastic event Formation Formation Outan Island Formation Nipigon Formation Recent Era of Great Mid-continent Basin Formation (MI, IL, IA, IN, KY, MO) 2 inches Marshfield Archean Gneiss (C WI) Linwood Archean Migmatite (C WI) Sudbury Dike Swarm (SE ON) Quinnesec Formation Intrusions (NE WI) Quinnesec Formation Metamorphism (NE WI) Hatfield Gneiss (WC WI) Pre-Quinnesec Formations deposited (NE WI) Upper Rove Formation Baraboo Quartzite LEGEND (Sibley Peninsula, Thunder Bay, ON) Gray granodioritic phase Montevideo Gneiss (SW MN) Red granite phase Montevideo Gneiss
    [Show full text]
  • Paleozoic Stratigraphic Nomenclature for Wisconsin (Wisconsin
    UNIVERSITY EXTENSION The University of Wisconsin Geological and Natural History Survey Information Circular Number 8 Paleozoic Stratigraphic Nomenclature For Wisconsin By Meredith E. Ostrom"'" INTRODUCTION The Paleozoic stratigraphic nomenclature shown in the Oronto a Precambrian age and selected the basal contact column is a part of a broad program of the Wisconsin at the top of the uppermost volcanic bed. It is now known Geological and Natural History Survey to re-examine the that the Oronto is unconformable with older rocks in some Paleozoic rocks of Wisconsin and is a response to the needs areas as for example at Fond du Lac, Minnesota, where of geologists, hydrologists and the mineral industry. The the Outer Conglomerate and Nonesuch Shale are missing column was preceded by studies of pre-Cincinnatian cyclical and the younger Freda Sandstone rests on the Thompson sedimentation in the upper Mississippi valley area (Ostrom, Slate (Raasch, 1950; Goldich et ai, 1961). An unconformity 1964), Cambro-Ordovician stratigraphy of southwestern at the upper contact in the Upper Peninsula of Michigan Wisconsin (Ostrom, 1965) and Cambrian stratigraphy in has been postulated by Hamblin (1961) and in northwestern western Wisconsin (Ostrom, 1966). Wisconsin wlle're Atwater and Clement (1935) describe un­ A major problem of correlation is the tracing of outcrop conformities between flat-lying quartz sandstone (either formations into the subsurface. Outcrop definitions of Mt. Simon, Bayfield, or Hinckley) and older westward formations based chiefly on paleontology can rarely, if dipping Keweenawan volcanics and arkosic sandstone. ever, be extended into the subsurface of Wisconsin because From the above data it would appear that arkosic fossils are usually scarce or absent and their fragments cari rocks of the Oronto Group are unconformable with both seldom be recognized in drill cuttings.
    [Show full text]
  • The End of Midcontinent Rift Magmatism and the Paleogeography of Laurentia
    THEMED ISSUE: Tectonics at the Micro- to Macroscale: Contributions in Honor of the University of Michigan Structure-Tectonics Research Group of Ben van der Pluijm and Rob Van der Voo The end of Midcontinent Rift magmatism and the paleogeography of Laurentia Luke M. Fairchild1, Nicholas L. Swanson-Hysell1, Jahandar Ramezani2, Courtney J. Sprain1, and Samuel A. Bowring2 1DEPARTMENT OF EARTH AND PLANETARY SCIENCE, UNIVERSITY OF CALIFORNIA, BERKELEY, CALIFORNIA 94720, USA 2DEPARTMENT OF EARTH, ATMOSPHERIC AND PLANETARY SCIENCES, MASSACHUSETTS INSTITUTE OF TECHNOLOGY, CAMBRIDGE, MASSACHUSETTS 02139, USA ABSTRACT Paleomagnetism of the North American Midcontinent Rift provides a robust paleogeographic record of Laurentia (cratonic North America) from ca. 1110 to 1070 Ma, revealing rapid equatorward motion of the continent throughout rift magmatism. Existing age and paleomagnetic constraints on the youngest rift volcanic and sedimentary rocks have been interpreted to record a slowdown of this motion as rifting waned. We present new paleomagnetic and geochronologic data from the ca. 1090–1083 Ma “late-stage” rift volcanic rocks exposed as the Lake Shore Traps (Michigan), the Schroeder-Lutsen basalts (Minnesota), and the Michipicoten Island Formation (Ontario). The paleomagnetic data allow for the development of paleomagnetic poles for the Schroeder-Lutsen basalts (187.8°E, 27.1°N; A95 = 3.0°, N = 50) and the Michipicoten Island Formation (174.7°E, 17.0°N; A95 = 4.4°, N = 23). Temporal constraints on late-stage paleomagnetic poles are provided by high-precision, 206Pb-238U zircon dates from a Lake Shore Traps andesite (1085.57 ± 0.25 Ma; 2σ internal errors), a Michipicoten Island Formation tuff (1084.35 ± 0.20 Ma) and rhyolite (1083.52 ± 0.23 Ma), and a Silver Bay aplitic dike from the Beaver Bay Complex (1091.61 ± 0.14 Ma), which is overlain by the Schroeder-Lutsen basalt flows.
    [Show full text]
  • Concretions Or Fossils?
    PALAIOS, 2016, v. 31, 327–338 Research Article DOI: http://dx.doi.org/10.2110/palo.2016.013 MACROSCOPIC STRUCTURES IN THE 1.1 Ga CONTINENTAL COPPER HARBOR FORMATION: CONCRETIONS OR FOSSILS? 1 1 2 1 3 ROSS P. ANDERSON, LIDYA G. TARHAN, KATHERINE E. CUMMINGS, NOAH J. PLANAVSKY, AND MARCIA BJØRNERUD 1Department of Geology and Geophysics, Yale University, 210 Whitney Avenue, New Haven, Connecticut 06511, USA 2Department of Natural History, University of Florida, Gainesville, Florida 32611, USA 3Geology Department, Lawrence University, Appleton, Wisconsin 54911, USA email: [email protected] ABSTRACT: Continental siltstones of the Mesoproterozoic Copper Harbor Formation, Michigan contain macroscopic structures of a size and morphological complexity commonly associated with fossils of eukaryotic macroorganisms. A biogenic origin for these structures would significantly augment the Proterozoic continental fossil record, which is currently poor, and also add to a growing body of sedimentological and geochemical data that, albeit indirectly, indicates the presence of life in continental settings early in Earth’s history. These three- dimensional structures occur abundantly within a single cm-scale siltstone bed. Along this bedding plane, these structures are generally circular-to-ovoid, range up to several centimeters in diameter, and most specimens possess a transecting lenticular element. Structures exhibit sharp, well-rounded external margins and, in contrast to the surrounding aluminosilicate-rich matrix, are calcitic in composition. Surrounding sedimentary laminae are deflected by and cross cut the structures. A fossiliferous origin is considered but rejected and an authigenic concretionary origin is favored based on these characters. However, a concretionary origin does not exclude the possibility of a biogenic precursor that served as a locus for early diagenetic calcite precipitation.
    [Show full text]
  • Contents Illustrations Table Introduction
    The Base of the Upper Keweenawan, ILLUSTRATIONS Michigan and Wisconsin FIGURE 1. Distribution of the Copper Harbor Conglomerate and included mafic lava members...........................................2 By WALTER S. WHITE 2. Stratigraphic section of the Copper Harbor Conglomerate..2 CONTRIBUTIONS TO STRATIGRAPHY 3. Longitudinal stratigraphic section of Keweenawan rocks below the base of the Nonesuch Shale............................3 4. Mean directions of magnetization for some Keweenawan GEOLOGICAL SURVEY BULLETIN 1354-F rocks.. ..............................................................................6 A proposal to adopt the top of the Copper Harbor 5. Proposed nomenclature for middle and upper Keweenawan Conglomerate as the base of the upper Keweenawan in rocks ................................................................................9 the Lake Superior region TABLE TABLE 1. Compressional wave velocities (km/sec) for selected Keweenawan stratigraphic units, Lake Superior region ...7 ABSTRACT UNITED STATES GOVERNMENT PRINTING OFFICE, The top of the Copper Harbor Conglomerate (base of WASHINGTON : 1972 Nonesuch Shale) is a more satisfactory boundary between upper and middle Keweenawan rocks in northern Michigan and UNITED STATES DEPARTMENT OF THE INTERIOR adjacent parts of Wisconsin than the various horizons that ROGERS G. B. MORTON, Secretary have been used hitherto without stratigraphic consistency from GEOLOGICAL SURVEY place to place. Irving’s original boundary (1883) cannot be V. E. McKelvey, Director followed away from the Keweenaw Peninsula. The top of the Copper Harbor Conglomerate comes closer to marking the Library of Congress catalog-card No. 72-75175 close of Keweenawan volcanism than other major boundaries and actually adheres more closely to Irving’s original concept For sale by the Superintendent of Documents, U.S. Government Printing Office than the boundary that he himself chose.
    [Show full text]
  • Petrography and Correlation of Precambrian Clastic Sedimentary Rocks Associated with the Midcontinent Rift System
    Petrography and Correlation of Precambrian Clastic Sedimentary Rocks Associated with the Midcontinent Rift System U.S. GEOLOGICAL SURVEY BULLETIN 1989-E AVAILABILITY OF BOOKS AND MAPS OF THE U.S. GEOLOGICAL SURVEY Instructions on ordering publications of the U.S. Geological Survey, along with prices of the last offerings, are given in the current-year issues of the monthly catalog "New Publications of the U.S. Geological Survey." Prices of available U.S. Geological Survey publications re­ leased prior to the current year are listed in the most recent annual "Price and Availability List." Publications that may be listed in various U.S. Geological Survey catalogs (see back inside cover) but not listed in the most recent annual "Price and Availability List" may no longer be available. Reports released through the NTIS may be obtained by writing to the National Technical Information Service, U.S. Department of Commerce, Springfield, VA 22161; please include NTIS report number with inquiry. Order U.S. Geological Survey publications by mail or over the counter from the offices listed below. BY MAIL OVER THE COUNTER Books Books and Maps Professional Papers, Bulletins, Water-Supply Papers, Tech­ Books and maps of the U.S. Geological Survey are available niques of Water-Resources Investigations, Circulars, publications over the counter at the following U.S. Geological Survey offices, all of general interest (such as leaflets, pamphlets, booklets), single of which are authorized agents of the Superintendent of Docu­ copies of Earthquakes & Volcanoes, Preliminary Determination of ments. Epicenters, and some miscellaneous reports, including some of the foregoing series that have gone out of print at the Superintendent of Documents, are obtainable by mail from ANCHORAGE, Alaska-Rm.
    [Show full text]
  • Petrology, Stratigraphy and Sedimentation of the Middle
    PETROLOGY, STRATIGRAPHY AND SEDIMENTATION OF THE MIDDLE PROTEROZOIC BAYFIELD GROUP, NORTHWESTERN WISCONSIN A THESIS SUBMITTED TO THE FACULTY OF THE GRADUATE SCHOOL OF THE UNIVERSITY OF MINNESOTA BY Kent Fred Adamson IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE December, 1997 © Kent Fred Adamson, 1997 Abstract The Bayfield Group (Middle Proterozoic, Lake Superior region) is composed of three formations which are, from oldest to youngest, the feldspatholithic to lithofeldspathic Orienta Formation; the quartz-arenitic Devils Island Sandstone; and the feldspatholithic Chequamegon Formation. The average QFL percentages are 69/17 /14 for the Orienta Formation, 95/4/1 for the Devils Island Sandstone, and 79/14/7 for the Chequamegon Formation. The large amounts of quartz and appreciable feldspar suggest that the primary provenance was older Early and Archean rocks. Diagenetic action on the Bayfield Group is evidenced by authigenic quartz, hematite, kaolinite, zeolite, and minor amounts of potassium feldspar. The average pore space of the sandstones in the Bayfield Group decreases with depth. Dissolution of potassium feldspar is the major factor in the development of minor secondary porosity. Accessory minerals show that "normal" zircon is the most prevalent form found within the non-opaque, non-micaceous suite. The presence of "normal" zircons suggests that a potential provenance was Keweenawan volcanics; some residence time in previously deposited rift sediments (such as the Oronto Group) may have occurred. The minor amount of other zircon varieties support the framework grain analyses that older Early Proterozoic and Archean sources were shedding major amounts of sediment into the depositional basin.
    [Show full text]
  • Description of Map Units for Port Wing/Solon Springs Quads in Wisconsin
    7/16/2007 Description of Map Units for Port Wing/Solon Springs quads in Wisconsin STRATIFIED ROCKS Phanerozoic Rocks Cms Mount Simon Sandstone- quartzose sandstone containing some thin interbedded shale Mesoproterozoic Rocks Keweenawan Supergroup Bayfield Group Ybc Chequamegon Sandstone – Red, brown, and white feldspathic sandstone, generally thick-bedded and commonly cross-bedded. Sparse interbeds of red shale and conglomerate Ybd Devils Island Sandstone – White to tan quartz arenite, generally thin-bedded. Cross-bedding and ripple marks are common Ybo Orienta Sandstone – Red, brown, and white feldspathic sandstone, cross-bedded in part. Sparse interbeds of red shale and conglomerate Yu Unnamed sandstone – East of Lake Owen fault, inferred from geophysical data Oronto Group Yof Freda Sandstone – Red, brown, and tan sandstone containing minor shale and conglomerate interbeds. Mostly fine- to medium- grained feldspathic and lithic arenite, commonly micaceous. Well- bedded and commonly crossbedded Yon Nonesuch Formation – Siltstone, shale, sandstone, mostly gray to black, some red units. No outcrops in the map area but extent and lithology of formation in Ashland syncline well-defined by numerous drillholes Yoc Copper Harbor Conglomerate – Red to brown conglomerate, sandstone, and siltstone. Conglomerates are generally massive to crudely bedded and contain rounded clasts as much as 50 cm in diameter of mostly felsic volcanic rocks. Sandstones are mostly lithic arenites containing dominantly volcanic grains, commonly 7/16/2007 trough cross-bedded. Conglomerates are mostly near the base and finer grained rocks in higher in section St. Croix Volcanic Group Minong Volcanics Yml Low-TiO2 flood basalts; locally ophitic; near top of section contains basalt flows with a composition similar to normal mid-ocean ridge basalt (N-MORB); contains a few conglomerate interbeds (more common on the southeast side of the Ashland syncline than on the northwest limb of the syncline) Ymh High-TiO2 basalt flows interlayered with andesite and rhyolite flows.
    [Show full text]
  • Maximum Depositional Age of the Neoproterozoic Jacobsville Sandstone, Michigan: Implications for the Evolution of the GEOSPHERE; V
    Research Note GEOSPHERE Maximum depositional age of the Neoproterozoic Jacobsville Sandstone, Michigan: Implications for the evolution of the GEOSPHERE; v. 12, no. 4 Midcontinent Rift doi:10.1130/GES01302.1 David H. Malone1, Carol A. Stein2, John P. Craddock3, Jonas Kley4, Seth Stein5, and John E. Malone6 6 figures; 1 table 1Department of Geography-Geology, Illinois State University, Normal, Illinois 61790-4400, USA 2Department of Earth & Environmental Sciences, University of Illinois at Chicago, Chicago, Illinois 60607-7059, USA 3Geology Department, Macalester College, St. Paul, Minnesota 55105, USA CORRESPONDENCE: cstein@ uic .edu 4Geowissenschaftliches Zentrum, Georg-August-Universität Göttingen, Goldschmidtstraße 3, 37077 Göttingen, Germany 5Department of Earth & Planetary Sciences, Northwestern University, Evanston, Illinois 60208, USA CITATION: Malone, D.H., Stein, C.A., Craddock, 6Geology Department, Augustana College, Rock Island, Illinois 61201, USA J.P., Kley, J., Stein, S., and Malone, J.E., 2016, Maximum depositional age of the Neoproterozoic Ja- cobsville Sandstone, Michigan: Implications for the evolution of the Midcontinent Rift: Geosphere, v. 12, ABSTRACT et al., 2007; Loewy et al., 2011; Bright et al., 2014). The east arm goes through no. 4, p. 1271–1282, doi:10.1130/GES01302.1. lower Michigan and extends southward to Alabama (Keller et al., 1982; Dickas A crucial constraint on the evolution of the ca. 1100 Ma Midcontinent Rift et al., 1992; Stein et al., 2014). Received 8 December 2015 Revision received 14 May 2016 (MCR) in North America comes from the Jacobsville Sandstone, Bayfield Although the MCR was previously thought to have formed by isolated mid- Accepted 20 June 2016 Group, and other equivalent sedimentary rocks (JBE) that overlie the volcanics plate volcanism and to have failed due to Grenville compression (Gordon and Published online 12 July 2016 and sediments deposited in the MCR basin near Lake Superior.
    [Show full text]
  • Structural Analysis and Interpretation of Deformation Along the Keweenaw Fault System West of Lake Gratiot, Keweenaw County, Michigan
    Michigan Technological University Digital Commons @ Michigan Tech Dissertations, Master's Theses and Master's Reports 2021 Structural Analysis and Interpretation of Deformation Along the Keweenaw Fault System West of Lake Gratiot, Keweenaw County, Michigan Sophie A. Mueller Michigan Technological University, [email protected] Copyright 2021 Sophie A. Mueller Recommended Citation Mueller, Sophie A., "Structural Analysis and Interpretation of Deformation Along the Keweenaw Fault System West of Lake Gratiot, Keweenaw County, Michigan", Open Access Master's Thesis, Michigan Technological University, 2021. https://doi.org/10.37099/mtu.dc.etdr/1167 Follow this and additional works at: https://digitalcommons.mtu.edu/etdr Part of the Geology Commons, and the Tectonics and Structure Commons STRUCTURAL ANALYSIS AND INTERPRETATION OF DEFORMATION ALONG THE KEWEENAW FAULT SYSTEM WEST OF LAKE GRATIOT, KEWEENAW COUNTY, MICHIGAN By Sophie A. Mueller A THESIS Submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE In Geology MICHIGAN TECHNOLOGICAL UNIVERSITY 2021 © 2021 Sophie A. Mueller This thesis has been approved in partial fulfillment of the requirements for the Degree of MASTER OF SCIENCE in Geology. Department of Geological and Mining Engineering and Sciences Thesis Co-Advisor: James M. DeGraff Thesis Co-Advisor: Chad Deering Committee Member: Jeremy Shannon Department Chair: Aleksey Smirnov Table of Contents List of figures .............................................................................................................................
    [Show full text]
  • University of Wisconsin-Extension GEOLOGICAL and NATURAL HISTORY SURVEY 3817 Mineral Point Road Madison, Wisconsin 53705
    University of Wisconsin-Extension GEOLOGICAL AND NATURAL HISTORY SURVEY 3817 Mineral Point Road Madison, Wisconsin 53705 M.. E.. Ostrom, State Geologist and Dir.ector GEOLOGIC SUMMARY OF THE ASHLAND 2-DEGREE QUADRANGLE by M.G. Mudrey, Jr'. Open-File Report 79-1 39 p. + 2 plates This report represents work performed by the Geological and Natural History Survey, and is released to the open files in the interest of making the information more readily available. This report has not been edited or reviewed for conformity with Geological and Natural History Survey standards and nomenclature. GEOLOGIC SUMMARY OF THE ASUhID 2' QUANDRANGLE M.G. Mudrey, Jr. Wisconsin Geological and Xztural History Survey Unitersity of Wisconsin-Extension 1815 University Avenue Madison, Wisconsin 53706 d University of Wisconsin-Extension MICHAEL G MUDREY, JR. ocoloprr GBOIOQ~CBI Na1~1aInlrtorr Svney Mr. John W. Arendt Union Carbide Corporation P.O. Box P Mail Stop 246 Oakridge, Tennessee 37830 Purchase Order Number ORGD 19K-97723V January 2, 1979 GEOLOGIC SUMMARY OF THE ASHLAND 2' QUADRANGLE Introduction...................... Physiographic Setting .............. Geologic Setting .................. Geologic Summary ................. d Lower Precambrian........... : ....... Middle Precambrian .................. Bad River Dolomite ................ Palms Formation .................. Ironwood Iron Formation ............. Tyler Formation ................. Intermixed Metasedimentary and Metavolcanic Rocks I Upper Precambrian .......................12 Lower Keweenawan Rocks
    [Show full text]