DOCSLIB.ORG

Stratigraphy and Sedimentation of the Proterozoic Garnet Range Formation Belt Supergroup Western Montana

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Stratigraphy and Sedimentation of the Proterozoic Garnet Range Formation Belt Supergroup Western Montana University of Montana ScholarWorks at University of Montana Graduate Student Theses, Dissertations, & Professional Papers Graduate School 1984 Stratigraphy and sedimentation of the Proterozoic Garnet Range formation Belt Supergroup western Montana Michael F. McGroder The University of Montana Follow this and additional works at: https://scholarworks.umt.edu/etd Let us know how access to this document benefits ou.y Recommended Citation McGroder, Michael F., "Stratigraphy and sedimentation of the Proterozoic Garnet Range formation Belt Supergroup western Montana" (1984). Graduate Student Theses, Dissertations, & Professional Papers. 7549. https://scholarworks.umt.edu/etd/7549 This Thesis is brought to you for free and open access by the Graduate School at ScholarWorks at University of Montana. It has been accepted for inclusion in Graduate Student Theses, Dissertations, & Professional Papers by an authorized administrator of ScholarWorks at University of Montana. For more information, please contact [email protected]. COPYRIGHT ACT OF 1975 Th is is an unpublished manuscript in w hich c o pyr ig ht sub ­ s i s t s . Any further r e p r in t in g of it s contents must be approved BY THE author . Ma n s f ie l d L ibrary Un iv e r s it y of Montana Date : _________1 - 9 ^ 4 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. STRATIGRAPHY AND SEDIMENTATION OF THE PR0TERO20IC GARNET RANGE FORMATION, BELT SUPERGROUP, WESTERN MONTANA By Michael F. McGroder B.S., University of C alifornia, Santa Cruz, 1980 presented in partial fulfillment of the requirements for the degree of Master of Science UNIVERSITY OF MONTANA 1984 Approved by ai rman, Boar‘s of Ex am i n e r s Dfah, Graduate School Date Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. UMI Number: EP38350 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. UMT OiMartation Publishing UMI EP38350 Published by ProQuest LLC (2013). Copyright in the Dissertation held by the Author. Microform Edition © ProQuest LLC. All rights reserved. This work is protected against unauthorized copying under Title 17, United States Code Pro uest ProQuest LLC. 789 East Eisenhower Parkway P.O. Box 1346 Ann Arbor, Ml 48106 -1346 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. McGroder, Michael F ., M.S., August, 1984 Geology Stratigraphy and Sedimentation of the Proterozoic Garnet Range Formation, Belt Supergroup, Western Montana <107 pp.) Director: Dr. Johnnie N. Moore The Middle<?) Proterozoic Garnet Range Formation of western Montana comprises the third and uppermost firs t-o rd e r transgress!ve sequence in the Belt Supergroup. I t was deposited as interbedded sandstone and mudstone in marine marginal, nearshore, and offshore environments on a broad, shallow marine platform. Sedimentary structures and textures distinguish four lithofacies. In ascending order, these are: 1) a thinly interlayered sandstone-mudstone facies, deposited in intertidal and subtidal settings; 2) a planar bedded sandstone facies with thin mud partings, probably formed on and between upper shoreface shoals; 3) a rhythmically bedded sandstone-mudstone facies with hummocky bedding, deposited on the lower shoreface during and between storms; and 4) a rhythmically bedded facies similar to facies 3, but with thinner mudstone interbeds and polymodally oriented megaripples, formed on the upper shoreface, in tidal channels, and<?> on beaches. Commonly, the micaceous, fine grained sandstone portion of facies 3 is tr ip a r tite — grading from plane bedded at the base to hummocky bedded at the top, and capped by wave ripples. This sequence suggests that storm currents began as largely unidirectional, gradually changed to largely oscillatory, and then waned. The Garnet Range represents the only documented storm dominated si 1iciclastic shelf deposits in approximately 15km of Belt rocks. Perhaps this signals the fir s t wholesale marine inundation of the Belt Basin late in its history. Submergence or tectonic translation of a western 1andmass may have caused this inundation, I I Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. TABLE OF CONTENTS Abstract i i List of F ig u r e s .......................................................................................................iv Acknowledgements. ................... v INTRODUCTION................................................................................................................... p . 1 CHAPTER ONE: STRATIGRAPHY AND SEDIMENTATION OF THE GARNET RANGE FORMATION...................................................................................................p .6 Regional D istribution. Correlation, and Thickness. .....................p . 6 Facies Descriptions. ................................................................................. ,p . 11 Faciès One: Thinly interlayered sandstone-mudstone facies.p .15 Facies Two: Planar bedded sandstone fa c ie s ....................................p .16 Facies Three: Cyclic hummocky bedded fa cies ..................................p .18 Facies Four: Hummocky and cross bedded f a c i e s . ..............p .25 Pi 1 cher Quartz i t e . .................................................... p .28 Depositions! Processes and Environments .............. ................p .31 Facies One: Thinly interlayered sandstone-mudstone fa c ie s .p .31 Facies Two: Planar bedded sandstone fa c ie s ....................................p .34 Facies Three: Cyclic hummocky bedded facies .p.37 Facies Four: Hummocky and cross bedded fa c ie s.................... p . 40 CHAPTER TWO: STRATI GRAPHIC SYNTHESIS.....................................................p .42 Transoression-Reoressi on............................................................................. .p .42 T i des .............. .......................................................................................................p .44 Storm deposits............................................................................................... .p. 45 Sedimentation, tectonics, and aoe of the too of the B e lt. .p .47 Summary.........................................................................................................................p .50 CHAPTER THREE: DYNAMICS OF STORM SEDIMENT TRANSPORT AND HUMMOCKY BEDDING FORMATION, GARNET RANGE FORMATION..............p .51 Evidence of episodic deposition ..............................................................p .54 Hummocky cross s tr a tific a tio........................................... n .........................p .59 The mudstone portion of sandstone-mudstone cycles. .p .62 Deposit ional model-hummocky bedded fa c ie s ........................................p .64 REFERENCES.......................................................................................................................p. 67 APPENDIX...........................................................................................................................p. 73 One : Methods ....................................... ...............................................................p .73 Two: Section locations (geographically, strat(graphically).p.74 Three: Measured sections .................................................................................p .84 Eddy Creek .......................................................................................... p , 85 Ellis Mountain........................................................................................ p .86 Ninemi l e ................................................................ ..............................................p .88 Stuart Peak ........................................................................................................p .89 Pi 1 cher Creek ................................................................ ..................................p .92 Johnson Gulch............................................. ........................................ p . 96 LaFray C r e e k . ..............................................................................p .101 Wisherd Bridge ...................................................................... .......................p. 106 I 11 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. List of Figures Figure 1: Location map of Belt Basin... .............................................................. .p .2 Figure 2: Stratigraphy of the Belt Supergroup near Missoula, Montana... .p .3 Figure 3: Generalized geologic map—Missoula and vicinity ........................p .7 Figure 4: Correlation diagram— GTarnet Range Formation .p .10 Figure 5: Characteristic stratigraphie sequences—Facies One ................p .13 Figure 6i Characteristic stratigraphie sequence—Facies Two ...................p .17 Figure 7; Characteristic stratigraphie sequence—Facies Three ..............p .19 Figure 8: Characteristic stratigraphie sequence—Facies Four .................p .26 Figure 9; Paleocurrent data, Garnet Range Fm.,
Load more

Recommended publications
  • Montana Forest Insect and Disease Conditions and Program Highlights
    R1-16-17 03/20/2016 Forest Service Northern Region Montata Department of Natural Resources and Conservation Forestry Division In accordance with Federal civil rights law and U.S. Department of Agriculture (USDA) civil rights regulations and policies, the USDA, its Agencies, offices, and employees, and institutions participating in or administering USDA programs are prohibited from discriminating based on race, color, national origin, religion, sex, gender identity (including gender expression), sexual orientation, disability, age, marital status, family/parental status, income derived from a public assistance program, political beliefs, or reprisal or retaliation for prior civil rights activity, in any program or activity conducted or funded by USDA (not all bases apply to all programs). Remedies and complaint filing deadlines vary by program or incident. Persons with disabilities who require alternative means of communication for program information (e.g., Braille, large print, audiotape, American Sign Language, etc.) should contact the responsible Agency or USDA’s TARGET Center at (202) 720-2600 (voice and TTY) or contact USDA through the Federal Relay Service at (800) 877-8339. Additionally, program information may be made available in languages other than English. To file a program discrimination complaint, complete the USDA Program Discrimination Complaint Form, AD-3027, found online at http://www.ascr.usda.gov/complaint_filing_cust.html and at any USDA office or write a letter addressed to USDA and provide in the letter all of the information requested in the form. To request a copy of the complaint form, call (866) 632-9992. Submit your completed form or letter to USDA by: (1) mail: U.S.
    [Show full text]
  • National Register of Historic Places Registration Form
    NPS Form 10-900 OMB No. 1024-0018 (Rev. Oct. 1990) United States Department of the Interior National Park Service NATIONAL REGISTER OF HISTORIC PLACES REGISTRATION FORM 1. Name of Property historic name: Dearborn River High Bridge other name/site number: 24LC130 2. Location street & number: Fifteen Miles Southwest of Augusta on Bean Lake Road not for publication: n/a vicinity: X city/town: Augusta state: Montana code: MT county: Lewis & Clark code: 049 zip code: 59410 3. State/Federal Agency Certification As the designated authority under the National Historic Preservation Act of 1986, as amended, I hereby certify that this _X_ nomination _ request for detenj ination of eligibility meets the documentation standards for registering properties in the National Register of Historic Places and meets the proc urf I and professional requirements set forth in 36 CFR Part 60. In my opinion, the property X_ meets _ does not meet the National Register Criterfi commend thatthis oroperty be considered significant _ nationally X statewide X locafly. Signa jre of oertifying officialn itle Date Montana State Historic Preservation Office State or Federal agency or bureau (_ See continuation sheet for additional comments. In my opinion, the property _ meets _ does not meet the National Register criteria. Signature of commenting or other official Date State or Federal agency and bureau 4. National Park Service Certification , he/eby certify that this property is: 'entered in the National Register _ see continuation sheet _ determined eligible for the National Register _ see continuation sheet _ determined not eligible for the National Register_ _ see continuation sheet _ removed from the National Register _see continuation sheet _ other (explain): _________________ Dearborn River High Bridge Lewis & Clark County.
    [Show full text]
  • Compilation of Reported Sapphire Occurrences in Montana
    Report of Investigation 23 Compilation of Reported Sapphire Occurrences in Montana Richard B. Berg 2015 Cover photo by Richard Berg. Sapphires (very pale green and colorless) concentrated by panning. The small red grains are garnets, commonly found with sapphires in western Montana, and the black sand is mainly magnetite. Compilation of Reported Sapphire Occurrences, RI 23 Compilation of Reported Sapphire Occurrences in Montana Richard B. Berg Montana Bureau of Mines and Geology MBMG Report of Investigation 23 2015 i Compilation of Reported Sapphire Occurrences, RI 23 TABLE OF CONTENTS Introduction ............................................................................................................................1 Descriptions of Occurrences ..................................................................................................7 Selected Bibliography of Articles on Montana Sapphires ................................................... 75 General Montana ............................................................................................................75 Yogo ................................................................................................................................ 75 Southwestern Montana Alluvial Deposits........................................................................ 76 Specifi cally Rock Creek sapphire district ........................................................................ 76 Specifi cally Dry Cottonwood Creek deposit and the Butte area ....................................
    [Show full text]
  • Hydrogeologic Framework of the Upper Clark Fork River Area: Deer Lodge, Granite, Powell, and Silver Bow Counties R15W R14W R13W R12W By
    Montana Bureau of Mines and Geology Montana Groundwater Assessment Atlas No. 5, Part B, Map 2 A Department of Montana Tech of The University of Montana July 2009 Open-File Version Hydrogeologic Framework of the Upper Clark Fork River Area: Deer Lodge, Granite, Powell, and Silver Bow Counties R15W R14W R13W R12W by S Qsf w Qsf Yb Larry N. Smith a n T21N Qsf Yb T21N R Authors Note: This map is part of the Montana Bureau of Mines and Geology (MBMG) a n Pz Pz Groundwater Assessment Atlas for the Upper Clark Fork River Area groundwater Philipsburg ValleyUpper Flint Creek g e Pz Qsf characterization. It is intended to stand alone and describe a single hydrogeologic aspect of the study area, although many of the areas hydrogeologic features are The town of Philipsburg is the largest population center in the valley between the Qsc interrelated. For an integrated view of the hydrogeology of the Upper Clark Fork Area Flint Creek Range and the John Long Mountains. The Philipsburg Valley contains 47o30 the reader is referred to Part A (descriptive overview) and Part B (maps) of the Montana 040 ft of Quaternary alluvial sediment deposited along streams cut into Tertiary 47o30 Groundwater Assessment Atlas 5. sedimentary rocks of unknown thickness. The east-side valley margin was glaciated . T20N Yb t R during the last glaciation, producing ice-sculpted topography and rolling hills in side oo B kf l Ovando c INTRODUCTION drainages on the west slopes of the Flint Creek Range. Prominent benches between ac la kf k B Blac oo N F T20N tributaries to Flint Creek are mostly underlain by Tertiary sedimentary rocks.
    [Show full text]
  • Southwest MONTANA Visitvisit Southwest MONTANA
    visit SouthWest MONTANA visitvisit SouthWest MONTANA 2016 OFFICIAL REGIONAL TRAVEL GUIDE SOUTHWESTMT.COM • 800-879-1159 Powwow (Lisa Wareham) Sawtooth Lake (Chuck Haney) Pronghorn Antelope (Donnie Sexton) Bannack State Park (Donnie Sexton) SouthWest MONTANABetween Yellowstone National Park and Glacier National Park lies a landscape that encapsulates the best of what Montana’s about. Here, breathtaking crags pierce the bluest sky you’ve ever seen. Vast flocks of trumpeter swans splash down on the emerald waters of high mountain lakes. Quiet ghost towns beckon you back into history. Lively communities buzz with the welcoming vibe and creative energy of today’s frontier. Whether your passion is snowboarding or golfing, microbrews or monster trout, you’ll find endless riches in Southwest Montana. You’ll also find gems of places to enjoy a hearty meal or rest your head — from friendly roadside diners to lavish Western resorts. We look forward to sharing this Rexford Yaak Eureka Westby GLACIER Whitetail Babb Sweetgrass Four Flaxville NATIONAL Opheim Buttes Fortine Polebridge Sunburst Turner remarkable place with you. Trego St. Mary PARK Loring Whitewater Peerless Scobey Plentywood Lake Cut Bank Troy Apgar McDonald Browning Chinook Medicine Lake Libby West Glacier Columbia Shelby Falls Coram Rudyard Martin City Chester Froid Whitefish East Glacier Galata Havre Fort Hinsdale Saint Hungry Saco Lustre Horse Park Valier Box Belknap Marie Elder Dodson Vandalia Kalispell Essex Agency Heart Butte Malta Culbertson Kila Dupuyer Wolf Marion Bigfork Flathead River Glasgow Nashua Poplar Heron Big Sandy Point Somers Conrad Bainville Noxon Lakeside Rollins Bynum Brady Proctor Swan Lake Fort Fairview Trout Dayton Virgelle Peck Creek Elmo Fort Benton Loma Thompson Big Arm Choteau Landusky Zortman Sidney Falls Hot Springs Polson Lambert Crane CONTENTS Condon Fairfield Great Haugan Ronan Vaughn Plains Falls Savage De Borgia Charlo Augusta Winifred Bloomfield St.
    [Show full text]
  • Redbeds of the Upper Entrada Sandstone, Central Utah
    Brigham Young University BYU ScholarsArchive All Theses and Dissertations 2016-12-01 Redbeds of the Upper Entrada Sandstone, Central Utah: Facies Analysis and Regional Implications of Interfingered Sabkha and Fluvial Terminal Splay Sediments Jeffery Michael Valenza Brigham Young University Follow this and additional works at: https://scholarsarchive.byu.edu/etd Part of the Geology Commons BYU ScholarsArchive Citation Valenza, Jeffery Michael, "Redbeds of the Upper Entrada Sandstone, Central Utah: Facies Analysis and Regional Implications of Interfingered Sabkha and Fluvial Terminal Splay Sediments" (2016). All Theses and Dissertations. 6112. https://scholarsarchive.byu.edu/etd/6112 This Thesis is brought to you for free and open access by BYU ScholarsArchive. It has been accepted for inclusion in All Theses and Dissertations by an authorized administrator of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. Redbeds of the Upper Entrada Sandstone, Central Utah: Facies Analysis and Regional Implications of Interfingered Sabkha and Fluvial Terminal Splay Sediments Jeffery Michael Valenza A thesis submitted to the faculty of Brigham Young University in partial fulfillment of the requirements for the degree of Master of Science Thomas H. Morris, Chair Jani Radebaugh Sam Hudson Scott M. Ritter Department of Geological Sciences Brigham Young University Copyright © 2016 Jeffery Michael Valenza All Rights Reserved ABSTRACT Redbeds of the Upper Entrada Sandstone, Central Utah: Facies Analysis and Regional Implications of Interfingered Sabkha and Fluvial Terminal Splay Sediments Jeffery Michael Valenza Department of Geological Sciences, BYU Master of Science First distinguished from other sedimentary successions in 1928, the Entrada Sandstone has been the subject of numerous studies.
    [Show full text]
  • Geologic Formations of Western Oregon
    BULLETIN 70 GEOLOGIC fORMATION§ OF WESTERN OREGON WEST OF LONGITUDE 121° 30' STATE OF OREGON DEPARTMENT OF GEOLOGY AND MINERAL INDUSTRIES 1971 STATE OF OREGON DEPARTMENT OF GEOLOGY AND MINERAL INDUSTRIES 1069 Stal·e Office Building Portland, Oregon 97201 BULLETIN 70 GEOLOGIC FORMATIONS OF WESTERN OREGON (WEST OF LONGITUDE 12 1 °30') By John D. Beaulieu 1971 GOVERNING BOARD Fayette I. Bristol, Rogue River, Chairman R. W. deWeese, Portland Harold Banta, Baker STATE GEOLOGIST R. E. Corcoran CONTENTS Introduction . Acknowledgements 2 Geologic formations 3 Quadrang I es. 53 Corre I ation charts. 60 Bibliography. 63 ii GE OLOGIC FORMA T IONS OF WESTERN OR EGON (W E ST OF LONG ITUD E 12 1°30') By John D. Beaulieu* INTRODUCTION It is the purpose of th is publi cation to provide a concise , yet comprehensive discussion of the for­ mations of western Oregon. It is the further aim that the data for each of the formations be as current as possi ble. Consequently, the emphasis has been placed on th e recent literature . Although this paper should not be viewed as a discussion of the historical development of each of the fo rmations, the original reference for each of the units is given . Also, in cases where the historical development of the formation has a direct bearing on present-day problems it is included in the discussion . A wide variety of published literature and unpublished reports , theses, and dissertations was con­ sul ted and several professional opin ions regarding specific problems were so licited . In recent years re­ search has been concentrated in the Klamath Mountains and the southern Coast Range and for these regions literature was volumi nous.
    [Show full text]
  • Evolution of the Cordilleran Foreland Basin System in Northwestern Montana, U.S.A
    Evolution of the Cordilleran foreland basin system in northwestern Montana, U.S.A. Facundo Fuentes†, Peter G. DeCelles, Kurt N. Constenius, and George E. Gehrels Department of Geosciences, University of Arizona, Tucson, Arizona 85721, USA ABSTRACT episode of marine inundation and black shale 1989; Fermor and Moffat, 1992; Stockmal et al., deposition (Marias River Shale) occurred be- 1992; Beaumont et al., 1993; Plint et al., 1993; New lithostratigraphic and chronostrati- tween the Cenomanian and mid-Santonian, Ross et al., 2005; Miall et al., 2008; Yang and graphic, geochronologic, and sedimentary and was followed by a regressive succession Miall, 2009). This bimodal focus was mainly petrologic data illuminate the history of represented by the Upper Santonian–mid- driven by either the presence of anomalously development of the North American Cor- Campanian Telegraph Creek, Virgelle, and good surface exposures, as in the case of the dilleran foreland basin system and adjacent Two Medicine Formations. Provenance data western interior United States, or by hydro- thrust belt from Middle Jurassic through do not resolve the timing of individual thrust carbon exploration and a large subsurface data- Eocene time in northwestern Montana. The displacements during Cenomanian–early base, as in Canada (Miall et al., 2008). The oldest deposits in the foreland basin system Campanian time. The Upper Campanian ~300-km-long segment of the foreland basin consist of relatively thin, regionally tabu- Bearpaw Formation represents the last major lying within and east of the Cordilleran belt in lar deposits of the marine Ellis Group and marine inundation in the foreland basin . By northwestern Montana remains comparatively fl uvial-estuarine Morrison Formation, which latest Campanian time, a major epi sode of poorly understood in terms of its stratigraphy, accumulated during Bajocian to Kimmerid- slip on the Lewis thrust system had com- basin evolution, and relationship with the kine- gian time.
    [Show full text]
  • The Future of Stream Access in Montana
    2017 The Best in the West: Stream Access in Montana Public Land/Water Access Association High Water by Mary J. Maxam By Brent Zundel For the Public Land/Water Access Association April 2017 Keeping the public on public lands and waters Overview Montana’s Stream Access Law is widely considered “the best in the west,” arguably the strongest law in the nation in terms of ensuring public access. In short, the public can access any river or stream capable of being used for recreation between the high-water marks, regardless of the navigability of the river or the ownership of the streambed and adjacent property, as long as the user avoids trespass in order to reach the stream. This document provides a history of stream access in Montana, beginning with the original conflicts on the Dearborn and Beaverhead Rivers and continuing to the recently decided battles over access at bridges and the most recent challenge to the Stream Access Law. Early conflicts in the late 1970s and early 1980s led to the groundbreaking Curran The Yellowstone River flows through Paradise Valley, south of Livingston, and Hildreth cases in the Montana. Photo courtesy Brent Zundel Montana Supreme Court. These cases laid the foundation for the groundbreaking 1985 Stream Access Law, which codifies the strong public access rights enjoyed by all Montanans today. Immediately upon passage of the law, it was challenged in district courts, the state supreme court, and even appealed to the federal level. It has withstood all challenges. In the past decade, those fighting against public access have shifted to focus on stream access at bridges, with much of the controversy centering on the iconic Ruby River.
    [Show full text]
  • Cambrian Shelf Deposits of the King Square Formation, Saint John Group, Southern New Brunswick Saifullah K
    Document generated on 09/26/2021 6:59 p.m. Atlantic Geology Cambrian shelf deposits of the King Square Formation, Saint John Group, southern New Brunswick Saifullah K. Tanoli and Ron K. Pickerill Volume 25, Number 2, August 1989 Article abstract The upper Middle Cambrian to early Late Cambrian King Square Formation, URI: https://id.erudit.org/iderudit/ageo25_2art03 Saint John Group, southern New Brunswick, is an approximately 380 m thick silicilastic sequence of interbedded fine-grained sandstones and siltstones and See table of contents shales. On the basis of sandstone to shale/siltstone ratios, bed thickness and characteristics, sedimentary structures and degree of bioturbation three lithofacies are recognized. These are facies KS1, thin bedded sandstone and Publisher(s) shale lithofacies; KS2, thick bedded sandstone lithofacies; and KS3, bioturbatcd shale and siltstone with interbedded sandstone lithofacies. These lithofacies Atlantic Geoscience Society are interpreted to havebeen deposited on a wave- and storm-influenced marine subtidal shelf. Facies KS 1 was deposited essentially below wave base ISSN though in its upper horizons, deposition may have occurred above storm wave base. Facies KS2 was essentially deposited in a shallower subtidal inner- to 0843-5561 (print) mid-shelf environment above storm wave base and facies KS3 initially above 1718-7885 (digital) and latterly below storm wave base. The exact nature of the currents responsible for transportation and deposition of the storm-related sandstones Explore this journal (geostrophic flows or turbidity currents) is impossible to determine and therefore palaeocurrent data must be interpreted with caution. The stratigraphic arrangement of the lithofacies, with facies KS1 being the oldest Cite this article and KS3 the youngest, suggests that the King Square Formation represents a regressive-transgressive sequence.
    [Show full text]
  • Controls on Ore Deposition, Polaris Mining District, Pioneer Mountains
    Controls on ore deposition, Polaris mining district, Pioneer Mountains, Beaverhead County, Montana by Thomas Edward Davis A thesis submitted in partial fulfullment of the requirements for the degree of MASTER OF SCIENCE in Earth Sciences Montana State University © Copyright by Thomas Edward Davis (1980) Abstract: The Polaris silver mining district is located along the southern margin of the Cretaceous Pioneer batholith. The silver ore replaces Mississippian age Madison Group limestone though in other districts of the Pioneer region Cambrian carbonates may also be mineralized. Other stratigraphic units present in the Pioneer district are the Precambrian Missoula Group and the Cambrian Meagher, Park, and Pilgrim Formations. These strata underwent six stages of faulting, probably during the Laramide orogeny. In chronological order, the fault systems strike: N 33° W; N-S; E-W; N 60° E; N 40° E; and N-S. A N-S fold set formed after the first stage of faulting, and an E-W fold set developed after all faulting. A third folding episode, evident only underground, has folded the Polaris (N 60° E) fault. The batholith intruded passively after the fifth and perhaps after the sixth episode of faulting. Ore mineralization is presumed to have followed intrusion of the batholith, at least of its deeper levels, by analogy with other ore districts in the Pioneer region. Ore replaces Madison Group limestone along N 60° E faults; only these faults were open at the time of mineralization since they were parallel to the direction of maximum stress. In the Polaris Mine, the principal mine of the district, the paragenetic sequence of mineralization is: pyrite, sphalerite; galena; pyrargyrite(?); and native silver.
    [Show full text]
  • Quaternary and Late Tertiary of Montana: Climate, Glaciation, Stratigraphy, and Vertebrate Fossils
    QUATERNARY AND LATE TERTIARY OF MONTANA: CLIMATE, GLACIATION, STRATIGRAPHY, AND VERTEBRATE FOSSILS Larry N. Smith,1 Christopher L. Hill,2 and Jon Reiten3 1Department of Geological Engineering, Montana Tech, Butte, Montana 2Department of Geosciences and Department of Anthropology, Boise State University, Idaho 3Montana Bureau of Mines and Geology, Billings, Montana 1. INTRODUCTION by incision on timescales of <10 ka to ~2 Ma. Much of the response can be associated with Quaternary cli- The landscape of Montana displays the Quaternary mate changes, whereas tectonic tilting and uplift may record of multiple glaciations in the mountainous areas, be locally signifi cant. incursion of two continental ice sheets from the north and northeast, and stream incision in both the glaciated The landscape of Montana is a result of mountain and unglaciated terrain. Both mountain and continental and continental glaciation, fl uvial incision and sta- glaciers covered about one-third of the State during the bility, and hillslope retreat. The Quaternary geologic last glaciation, between about 21 ka* and 14 ka. Ages of history, deposits, and landforms of Montana were glacial advances into the State during the last glaciation dominated by glaciation in the mountains of western are sparse, but suggest that the continental glacier in and central Montana and across the northern part of the eastern part of the State may have advanced earlier the central and eastern Plains (fi gs. 1, 2). Fundamental and retreated later than in western Montana.* The pre- to the landscape were the valley glaciers and ice caps last glacial Quaternary stratigraphy of the intermontane in the western mountains and Yellowstone, and the valleys is less well known.
    [Show full text]