FIELD GEOLOGY GUIDEBOOK AND NOTES ILLINOIS STATE UNIVERSITY 2016 Version 2 TABLE OF CONTENTS COURSE PURPOSE AND OBJECTIVES...............................................................................................5 Purpose and Description of Course ............................................................................................5 Course Objectives and Expected Outcomes ..............................................................................5 Course Schedule .........................................................................................................................6 How Friends and Family Can Contact You ...............................................................................7 COURSE POLICIES ...........................................................................................................................8 Course Policies...........................................................................................................................8 Safe and Respectful Field Practices ...........................................................................................8 Grading Policies .........................................................................................................................9 GEOLOGIC FIELD NOTES ..............................................................................................................10 Reconnaissance Notes ..............................................................................................................10 Measuring Stratigraphic Column Notes ...................................................................................11 Geologic Mapping Notes .........................................................................................................12 GEOLOGIC MAPS AND MAPPING ...................................................................................................15 Variables affecting the appearance of a geologic map .............................................................16 Techniques to test the quality and accuracy of your map ........................................................16 Common map errors ................................................................................................................17 Official USGS map colors .......................................................................................................17 Rule of V’s ...............................................................................................................................18 GEOLOGIC CROSS SECTIONS ........................................................................................................19 Basic principles of cross section construction .........................................................................19 Apparent dips: correct use of strike and dip data in cross sections .........................................20 Common cross section errors ...................................................................................................20 Steps in making a topographic profile for a geologic cross section .........................................21 Constructing geologic cross sections using down-plunge projection ......................................22 PROJECT 2: GEOLOGY OF THE AMSDEN CREEK BIG GAME WINTER RANGE PROJECT 3: GEOLOGY NEAR THE CLEAR CREEK THRUST ON STEERHEAD RANCH PHANEROZOIC STRATIGRAPHY OF NORTH AMERICA ..................................................................26 TECTONIC HISTORY OF THE U.S. CORDILLERA ...........................................................................31 Regional Cross-section Through Wyoming .............................................................................34 Wyoming Stratigraphic Nomenclature Chart ...........................................................................35 Rock Sequence in the Bighorn Basin .......................................................................................36 Rock Sequence in the Powder River Basin ..............................................................................37 Generalized Stratigraphic Column of the Bighorn Basin ........................................................38 BLACK HILLS GEOLOGY ...............................................................................................................39 Composite Stratigraphic Sections of the Black Hills Area ......................................................43 TERTIARY IGNEOUS ROCKS OF THE BLACK HILLS REGION .......................................................45 Style and geometry of typical igneous intrusions in the Black Hills region ............................50 PROJECT DESCRIPTIONS ...............................................................................................................51 Regional Stratigraphy...............................................................................................................51 Amsden Creek Big Game Winter Range .................................................................................53 3 Steerhead Ranch .......................................................................................................................54 Alikali Anticline.......................................................................................................................57 Heart Mountain Detachment ....................................................................................................59 Rochford ..................................................................................................................................64 APPENDIX 1: ESSENTIAL ANALYSIS TOOLS AND TECHNIQUES FOR FIELD GEOLOGY ...............65 Field description of rocks .........................................................................................................65 Measuring stratigraphic sections ..............................................................................................72 Calculating layer thicknesses ...................................................................................................79 Alignment diagram for calculating apparent dip .....................................................................80 Calculating strike and dip of a surface from contacts on a map ..............................................81 Calculating outcrop patterns from field observations - constructing a map ............................82 APPENDIX 2: GENERAL GUIDELINES FOR MAP PREPARATION ...................................................84 APPENDIX 3: GENERAL GUIDELINES FOR CROSS SECTION CONSTRUCTION .............................86 APPENDIX 4: STANDARD GEOLOGIC SYMBOLS AND PATTERNS .................................................88 APPENDIX 5: GEOLOGIC TIME SCALE .........................................................................................90 APPENDIX 6: BASIC FIRST AID ADVICE AND TREATMENT PROCEDURES ..................................91 APPENDIX 7: FIELD GUIDE TO THE HEART MOUNTAIN DETACHMENT ...................................110 APPENDIX 8: ADDITIONAL NOTES ON FIELD SAFETY……………………….......……………135 APPENDIX 9: POLICY FOR FIELD CAMP DISMISSAL……………...………….......……………142 4 COURSE PURPOSE AND OBJECTIVES Purpose and Description of Course The primary purpose of this course is to instruct students in the techniques of field geology and geologic mapping. The course is an intensive six-week program taught in the Black Hills of South Dakota, the central Bighorn Mountains, the Eastern Absaroka Range, and the Bighorn Basin of Wyoming. Students spend six days a week in the field, working independently and in groups to collect a variety of observational data and construct geologic maps of various assigned areas. At the conclusion of each project, students transform their rough field maps and observational data into a refined description of the geology of the mapped area. This description typically consists of a colored geologic map, geologic cross sections and descriptions of rock units exposed in the map area. This course is viewed as a capstone course for Geology programs because field geology is totally integrative, requiring students to make observations and interpretations concerning stratigraphic, sedimentologic, petrologic, paleontologic, metamorphic and structural characteristics of the rocks they encounter. At the same time, students must continually develop multiple working hypotheses about the distribution of rocks and geologic features in the areas they are mapping. In making a map, these hypotheses are iteratively tested and revised until a final interpretation of the map area is completed. This is the ultimate application of the scientific method! Course Objectives and Expected Outcomes The objectives of field camp are two-fold. In the simplest sense students must learn or be reacquainted with, and master several methods for qualitatively and quantitatively describing rocks in the field. These techniques include: (1) using the Brunton compass, measuring geologic sections, describing rocks, taking field notes, making geologic maps and cross sections and making field sketches, and (2) locating oneself on topographic maps and being able to recognize and interpret features on maps. In the larger sense, students completing this course should be able to “think on their feet”, and to apply the scientific method in real time to solve a variety of practical geologic problems. As examples, the student leaving field camp should be able to: (1) use their basic knowledge of geology to recognize and accurately record significant