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Fort Union National Monument Geologic Resources Inventory Report

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Fort Union National Monument Geologic Resources Inventory Report National Park Service U.S. Department of the Interior Natural Resource Stewardship and Science Fort Union National Monument Geologic Resources Inventory Report Natural Resource Report NPS/NRSS/GRD/NRR—2012/580 ON THE COVER Local materials, such as sandstone exposed in nearby cliffs and clay from the “adobe fields,” were used in the construction of Fort Union. Graneros Shale (geologic map unit Kgs), which underlies most of the national monument, yielded the clay. Dakota Sandstone (Kd) provided the building stone. Photograph by Katie KellerLynn (Colorado State University). THIS PAGE The Turkey Mountains fill the northern horizon at Fort Union National Monument. The mountains are composed of an igneous intrusion called a “laccolith.” Photograph by Katie KellerLynn (Colorado State University). Fort Union National Monument Geologic Resources Inventory Report Natural Resource Report NPS/NRSS/GRD/NRR—2012/580 National Park Service Geologic Resources Division PO Box 25287 Denver, CO 80225 September 2012 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. 2012. Fort Union National Monument: Geologic resources inventory report. Natural Resource Report NPS/NRSS/GRD/NRR—2012/580. National Park Service, Fort Collins, Colorado, USA. NPS 402/117052, September 2012 ii NPS Geologic Resources Division Contents List of Figures ................................................................................................................ iv Executive Summary ....................................................................................................... v Acknowledgments ....................................................................................................... vii Credits ....................................................................................................................................................................... viii Introduction ................................................................................................................... 1 Geologic Resources Inventory Program ......................................................................................................................... 1 Park Setting ................................................................................................................................................................. 1 Geologic Issues .............................................................................................................. 7 Soil Ruts ...................................................................................................................................................................... 7 Wolf Creek .................................................................................................................................................................. 8 Landslides and Rockfall ................................................................................................................................................ 9 Seismic Activity .......................................................................................................................................................... 10 Oil and Gas Development .......................................................................................................................................... 11 Geologic Features and Processes ................................................................................ 13 Volcanic Features ....................................................................................................................................................... 13 Dakota Sandstone ..................................................................................................................................................... 14 Turkey Mountains ...................................................................................................................................................... 15 Caves......................................................................................................................................................................... 16 Eolian Features and Processes .................................................................................................................................... 16 Building Materials ...................................................................................................................................................... 17 Stream Terraces ......................................................................................................................................................... 18 Paleontological Resources .......................................................................................................................................... 18 Geologic History .......................................................................................................... 19 Mesozoic Era: From Land to Seaway .......................................................................................................................... 19 Mesozoic and Cenozoic Eras: Laramide Orogeny ........................................................................................................ 20 Cenozoic Era: The End of Laramide Mountain Building and Beginning of Rio Grande Rifting ....................................... 20 Cenozoic Era: Volcanism Abounds ............................................................................................................................. 20 Cenozoic Era: The Present-Day Landscape .................................................................................................................. 20 Geologic Map Data ...................................................................................................... 23 Geologic Maps .......................................................................................................................................................... 23 Source Maps .............................................................................................................................................................. 23 Geologic GIS Data ..................................................................................................................................................... 23 Geologic Map Overview Graphic ................................................................................................................................ 24 Map Unit Properties Table .......................................................................................................................................... 24 Use Constraints .......................................................................................................................................................... 24 Glossary ........................................................................................................................ 25 Literature Cited ............................................................................................................ 29 Additional References ................................................................................................. 33 Geology of National Park Service Areas ...................................................................................................................... 33 NPS Resource Management Guidance and Documents ............................................................................................... 33 Geological Surveys and Societies ...............................................................................................................................
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