National Park Service U.S. Department of the Interior Natural Resource Stewardship and Science Bighorn Canyon National Recreation Area Geologic Resources Inventory Report Natural Resource Report NPS/NRSS/GRD/NRR—2011/447 ON THE COVER Exposed rocks within Bighorn Canyon National Recreation Area near Bull Elk Canyon. Photograph courtesy of David Lopez (geologist/consultant). THIS PAGE The sediment-laden Bighorn River winds its way through Bighorn Canyon. National Park Service photograph by Tim Connors (NPS Geologic Resources Division). Bighorn Canyon National Recreation Area Geologic Resources Inventory Report Natural Resource Report NPS/NRSS/GRD/NRR—2011/447 National Park Service Geologic Resources Division PO Box 25287 Denver, CO 80225 September 2011 U.S. Department of the Interior National Park Service Natural Resource Stewardship and Science Fort Collins, Colorado The National Park Service, Natural Resource Stewardship and Science office in Fort Collins, Colorado publishes a range of reports that address natural resource topics of interest and applicability to a broad audience in the National Park Service and others in natural resource management, including scientists, conservation and environmental constituencies, and the public. The Natural Resource Report Series is used to disseminate high-priority, current natural resource management information with managerial application. The series targets a general, diverse audience, and may contain NPS policy considerations or address sensitive issues of management applicability. All manuscripts in the series receive the appropriate level of peer review to ensure that the information is scientifically credible, technically accurate, appropriately written for the intended audience, and designed and published in a professional manner. This report received informal peer review by subject-matter experts who were not directly involved in the collection, analysis, or reporting of the data. Views, statements, findings, conclusions, recommendations, and data in this report do not necessarily reflect views and policies of the National Park Service, U.S. Department of the Interior. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the U.S. Government. Printed copies of this report are produced in a limited quantity and they are only available as long as the supply lasts. This report is available from the Geologic Resources Inventory website (http://www.nature.nps.gov/geology/inventory/ gre_publications.cfm) and the Natural Resource Publications Management website (http://www.nature.nps.gov/publications/nrpm/). Please cite this publication as: KellerLynn, K. 2011. Bighorn Canyon National Recreation Area: geologic resources inventory report. Natural Resource Report NPS/NRSS/GRD/NRR—2011/447. National Park Service, Fort Collins, Colorado, USA. NPS 617/110188, September 2011 ii NPS Geologic Resources Division Contents Lists of Figures and Tables ........................................................................................... iv Executive Summary ....................................................................................................... v Acknowledgements ..................................................................................................... vii Credits ....................................................................................................................................................................... vii Introduction ................................................................................................................... 1 Purpose of the Geologic Resources Inventory ............................................................................................................... 1 Regional Information ................................................................................................................................................... 1 Geologic Issues .............................................................................................................. 5 Sedimentation ............................................................................................................................................................. 5 Mineral Resources and Mining ..................................................................................................................................... 6 Abandoned Mineral Lands ........................................................................................................................................... 7 Other Disturbed Lands ................................................................................................................................................. 8 Mass Wasting .............................................................................................................................................................. 8 Flooding ...................................................................................................................................................................... 9 Frost Heaving and Shrink-Swell Potential ...................................................................................................................... 9 Geologic Features and Processes ................................................................................ 11 Bighorn Lake and Yellowtail Dam ............................................................................................................................... 11 Fluvial Features and Processes .................................................................................................................................... 12 Superimposed, Entrenched, Abandoned Meanders ..................................................................................................... 12 Terraces ..................................................................................................................................................................... 13 Seeps and Springs ...................................................................................................................................................... 13 Eolian Features and Processes..................................................................................................................................... 14 Structural and Tectonic Features and Processes........................................................................................................... 14 Caves and Karst ......................................................................................................................................................... 15 Paleokarst .................................................................................................................................................................. 16 Paleontological Resources .......................................................................................................................................... 17 Geologic History .......................................................................................................... 23 Archean Eon (4 billion to 2.5 billion years ago): Ancient Continental Crust .................................................................. 23 Paleozoic Era (542 million to 251 million years ago): Thick Package of Marine Sediments ............................................ 23 Mesozoic Era (251 million to 65.5 million years ago): Seas Displaced by Mountain Uplift ............................................. 24 Cenozoic Era (65.5 million years ago to present day): Creation of Bighorn Canyon ...................................................... 24 Geologic Map Data ...................................................................................................... 29 Geologic Maps ........................................................................................................................................................... 29 Source Maps .............................................................................................................................................................. 29 Geologic GIS Data ...................................................................................................................................................... 29 Geologic Map Overview ............................................................................................................................................. 30 Map Unit Properties Table .......................................................................................................................................... 30 Use Constraints .......................................................................................................................................................... 30 Geologic Map Overview Graphics .............................................................................. 31 Map Unit Properties Table .......................................................................................... 36 Glossary ........................................................................................................................ 43 Literature Cited ............................................................................................................ 49 Additional References ................................................................................................. 54 Appendix: Scoping Session Participants ...................................................................