National Park Service U.S. Department of the Interior Natural Resource Program Center Saguaro National Park Geologic Resources Inventory Report Natural Resource Report NPS/NRPC/GRD/NRR—2010/233 THIS PAGE: A Saguaro silhouette stands before the glow of a peerless Arizona sunset. ON THE COVER: View from Amole Peak over the Tuc- son Mountain District. This district of the park offers excellent exposures of the Tucson Mountains Caldera, the eroded remains of a colossal volcanic eruption that occurred approximately 70 to 75 million years ago. National Park Service photographs. Saguaro National Park Geologic Resources Inventory Report Natural Resource Report NPS/NRPC/GRD/NRR—2010/233 Geologic Resources Division Natural Resource Program Center P.O. Box 25287 Denver, Colorado 80225 August 2010 U.S. Department of the Interior National Park Service Natural Resource Program Center Ft. Collins, Colorado The National Park Service, Natural Resource Program Center 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: Graham, J. 2010. Saguaro National Park: geologic resources inventory report. Natural Resource Report NPS/NRPC/GRD/NRR—2010/233. National Park Service, Ft. Collins, Colorado. NPS 151/105455, August 2010 ii NPS Geologic Resources Division Contents Lists of Figures and Tables ........................................................................................... iv Executive Summary ....................................................................................................... v Acknowledgements ...................................................................................................... vi Credits ........................................................................................................................................................................ vi Introduction ................................................................................................................... 1 Purpose of the Geologic Resources Inventory ............................................................................................................... 1 Regional Location and Geologic Setting ....................................................................................................................... 1 Park History ................................................................................................................................................................. 2 Geologic Issues .............................................................................................................. 9 Hydrogeology .............................................................................................................................................................. 9 Abandoned Mineral Lands ......................................................................................................................................... 11 Interpretive Trail to the Santa Catalina Fault................................................................................................................ 13 Additional Mapping in the Rincon Mountain District ................................................................................................... 13 Other Issues ............................................................................................................................................................... 13 Geologic Features and Processes ................................................................................ 17 Rincon Mountain District ............................................................................................................................................ 17 Tucson Mountain District ........................................................................................................................................... 19 Map Unit Properties .................................................................................................... 27 Geologic History .......................................................................................................... 39 Precambrian (prior to 542 million years ago) ............................................................................................................... 39 Paleozoic Era (542 to 251 million years ago) ............................................................................................................... 39 Mesozoic Era (251 to 65.5 million years ago) .............................................................................................................. 40 Cenozoic Era (the past 65.5 million years) ................................................................................................................... 42 Glossary ........................................................................................................................ 51 Literature Cited ............................................................................................................ 55 Additional References ................................................................................................. 59 Appendix A: Overviews of Digital Geologic Data ..................................................... 60 Appendix B: Scoping Meeting Participants ................................................................ 63 Attachment 1: Geologic Resources Inventory Products CD SAGU Geologic Resources Inventory Report iii List of Figures Figure 1. Location maps for Saguaro National Park........................................................................................................... 4 Figure 2. Landform map of the Southwestern United States ............................................................................................. 5 Figure 3. Generalized stratigraphic column for rock units within the borders of Saguaro National Park ............................. 6 Figure 4. Cross-sectional view (A) and block diagram (B) of the metamorphic core complex .............................................. 7 Figure 5. Tanque Verde Ridge from the Loma Verde Trail, Rincon Mountain District ......................................................... 8 Figure 6. Welded tuff of the Cat Mountain Tuff forms cliffs at Gates Pass ........................................................................ 8 Figure 7. Riparian vegetation along Rincon Creek in the Rincon Mountain District .......................................................... 15 Figure 8. The Old Yuma Mine (ruins visible in photo) ...................................................................................................... 15 Figure 9. Vanadinite, one of many minerals mined from the Old Yuma Mine .................................................................. 16 Figure 10. Flash flooding in Tanque Verde Wash inundates Tanque Verde Loop Road..................................................... 16 Figure 11. Santa Catalina Fault surface exposed near Cactus Forest Drive in the Rincon Mountain District ....................... 23 Figure 12. Lower-plate rocks of Catalina Gneiss at the Javelina Rocks, Rincon Mountain District ..................................... 24 Figure 13. Minerals in the Catalina Gneiss are conspicuously banded.............................................................................. 24 Figure 14. Location of the Javelina Fault in relation to the Santa Catalina Fault Complex, Rincon Mountain District ......... 25 Figure 15. Evolution of the Tucson Mountains Caldera and deposition of the Cat Mountain Tuff .................................... 26 Figure 16. Horst and graben structure of the Basin-and-Range province ......................................................................... 26 Figure 17. Geologic timescale. ....................................................................................................................................... 28 Figure 18. Cambrian paleogeographic map of