Northwest Geology The Journal of The Tobacco Root Geological Society Volume 47, July 2018 43rd Annual Field Conference Southwest Montana Geology from the Helena Salient to the Drainages Connecting Yellowstone Park July 27–29, 2018 Two-million-year old basalt flow near Gardiner, Montana thought to represent an early phase of volcanism associated with Yellowstone eruptions. Photo by Alan English. Published by The Tobacco Root Geological Society, Inc. P.O. 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P.O. Box 118 Butte, Montana 59703 http://trgs.org Edited by: Sandy Underwood and Katie McDonald i The Tobacco Root Geological Society, Inc. P.O. Box 118 Butte, Montana 59703 Offi cers, 2017: President: Jesse Mosolf, Montana Bureau of Mines and Geology, Butte, MT Vice-President: William M. Phillips, Idaho Geological Survey, Moscow, ID Treasurer: Katie McDonald, Montana Bureau of Mines and Geology, Butte, MT Secretary: Emily Geraghty Ward, Rocky Mountain College, Billings, MT Corresponding Secretary: Lara Strickland, Columbus, MT Webmasters: Petr Yakovlev (Butte, MT) Board of Directors, 2017: Ted Antonioli, Geologist, Missoula, MT Bruce E. Cox, Geologist (semi-retired), Missoula, MT Larry Johnson, Consultant, Missoula, MT Larry N. Smith, Dept. of Geological Engineering, Montana Tech, Butte, MT Mike Stickney, Montana Bureau of Mines and Geology, Butte, MT Robert C. Thomas, Dept. of Environmental Sciences, U. of Montana-Western, Dillon, MT Emily Geraghty Ward, Geology Dept., Rocky Mountain College, Billings, MT 2018 Conference Organizers: Sandy Underwood, John Childs, and David R. Lageson, Bozeman, Montana Editors: Sandy Underwood and Katie McDonald (MBMG) Layout and Editing: Susan Barth (MBMG) Printed by Insty-Prints, Butte, Montana ISSN: 0096-7769 © 2017 The Tobacco Root Geological Society, Inc. http://trgs.org ii N G The Journal of The Tobacco Root Geological Society Volume 47, July 2018 Southwest Montana Geology from the Helena Salient to the Drainages Connecting Yellowstone Park TABLE OF CONTENTS Francis Ö. Dudás Xenoliths in the northern Crazy Mountains: Constraining magma yield strength from fi eld observations ......................................................................................................................................... 1 Rose and Waren Geology of Big Sky, Montana: Road log .............................................................................................29 Alan R. English Geology and thermal features of the Gardiner Basin, Park County, Montana ....................................37 Schmidt, Whisner, and Road log to the structural geology of the Lewis and Clark State Park and surrounding area, Whisner southwestern Montana: Some new ideas and more questions ............................................................41 Kalakay, Webber, and Geometry and kinematics of the Paradise shear zone, part of a major suture zone within the Lageson Wyoming province of southwest Montana ..........................................................................................69 FIELD GUIDES Francis Ö. Dudás Road log to xenolith localities in the northern Crazy Mountains ........................................................79 iii TRGS 2018 SCHOLARSHIP AWARD WINNERS • Alexander Brown (Foster), Montana Tech Understanding the geology and geochemistry of ore formation at the Golden Chest Mine • Garett Brown (TRGS), University of Georgia Testing for ecological gradients in the lower Mississippian Lodgepole Formation, Montana, USA • Andrew Del Turco (Harrison), Stockton University Thermodynamic evolution of the Wyoming Province: Application of quartz c-axis analysis to constrain the kinematics and temperature of deformation recorded in the Jewel Lake quartzite, southwestern Montana • Alexander Flores (Kleinkopf), Stockton University Petrophysical characterization of the North Snowy Block, southwestern Montana: Application of rock magnetism to understanding Precambrian tectonics • Richard M. Hess (TRGS), University of Georgia The Sequence stratigraphic architecture of the Upper and Middle Jurassic Stump and Preuss Formations, Western Wyoming and Eastern Idaho, USA • Leah Houser (TRGS), Utah State University Textural and thermochronologic constraints on the role of friction generated heat on silica-rich fault mirror surfaces of the Brigham City Segment, Wasatch fault zone, Utah • Kimberly Kramer (TRGS), Washington State University Quantifying paleo-peak geothermal fi eld gradients within three ranges in eastern Nevada • Derek Lichtner (TRGS), University of Wyoming Assessing sediment preservation completeness using mass conservation and depositional signal inversion: Wasatch Formation, southwest Wyoming • Evan Martin (TRGS), University of Idaho Assessing the topographic evolution of the North American Cordillera in Idaho, Wyoming and Montana during Tertiary time • Sierra Swenson (Skipp), University of Georgia, Athens Integrated sequence stratigraphy and paleobiology of the Sundance Seaway, Montana, USA • Jacob Thacker (TRGS), University of New Mexico The spatiotemporal evolution of Laramide deformation: An integrated geologic and thermochronologic study • Matthew Wanker (TRGS), Indiana University Dynamics of sediment transport through a river bifurcation iv TRGS HAMMER AWARD TRGS CHARTER MEMBERS RECIPIENTS Stanley W. Anderson Clyde Cody William S. Cordua Awarded for distinguished achievement Lanny H. Fisk in the study of the geology of the Richard I. Gibson† Northern Rocky Mountains Thomas Hanley Stephen W. Henderson 1993: Ed Ruppel* Thomas E. Hendrix 1994: Dick Berg Mac R. Hooton Inda Immega 2003: Don Winston Steven W. Koehler 2004: Dean Kleinkopf* Marian Millen Lankston† 2009: Betty Skipp Robert W. Lankston† 2010: Jim Sears J. David Lazor Joe J. Liteheiser, Jr. 2011: John Childs Judson Mead* 2012: J. Michael O’Neill Marvin R. Miller 2013: Paul Karl Link Vicki M. Miller* Allen H. Nelson 2014: Reed Lewis Alfred H. Pekarek 2015: Jeff Lonn Patricia Price* 2016: Bruce Cox Donald L. Rasmussen Raymond M. Rene TRGS HONORARY MEMBERS 1980: Charles J. Vitaliano* TRGS LIFETIME MEMBERS 2008: Elizabeth Younggren John Childs (also honorary Board member) Rob Foster 2010: Dick Berg Joan (Mrs. Jack) Harrison* Karen Keefer 2010: Bruce Cox Layaka Mann 2010: Dean Kleinkopf* Chris Pool 2010: Dave Lageson 2011: Marie Marshall Garsjo 2011: Paul Link 2011: Rob Thomas † = co-founder 2012: Jeff Lonn * = deceased 2012: Mitch Reynolds 2013: