National Park Service U.S. Department of the Interior Natural Resource Program Center Padre Island National Seashore Geologic Resources Inventory Report Natural Resource Report NPS/NRPC/GRD/NRR—2010/246 THIS PAGE: Padre Island National Seashore is home to a variety of sea turtles. The Kemp’s ridley sea turtle (pictured) is the smallest. Radio transmitters help researchers track turtle populations. ON THE COVER: Dunes on Padre Island National Sea- shore. The park was established to preserve one of the last undeveloped barrier islands in the United States. National Park Service photographs by Rebecca Beavers (NPS Geologic Resources Division). Padre Island National Seashore Geologic Resources Inventory Report Natural Resource Report NPS/NRPC/GRD/NRR—2010/246 Geologic Resources Division Natural Resource Program Center P.O. Box 25287 Denver, Colorado 80225 September 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: KellerLynn, K. 2010. Padre Island National Seashore: geologic resources inventory report. Natural Resource Report NPS/NRPC/GRD/NRR—2010/246. National Park Service, Ft. Collins, Colorado. NPS 613/105619, September 2010 ii NPS Geologic Resources Division Contents List of Figures ................................................................................................................ iv List of Tables ................................................................................................................. iv Executive Summary ....................................................................................................... v Acknowledgements ...................................................................................................... vi Credits ........................................................................................................................................................................ vi Introduction ................................................................................................................... 1 Purpose of the Geologic Resources Inventory ............................................................................................................... 1 Park Setting ................................................................................................................................................................. 1 Padre Island History ...................................................................................................................................................... 2 Geologic Issues .............................................................................................................. 5 Coastal Vulnerability .................................................................................................................................................... 5 Blowing Sand and Dune Development ......................................................................................................................... 6 Hurricanes ................................................................................................................................................................... 7 Benthic Habitat Mapping ............................................................................................................................................. 7 Paleontological Resources ............................................................................................................................................ 8 Bird Island Basin ........................................................................................................................................................... 9 Vehicle Impacts ............................................................................................................................................................ 9 Dredging ................................................................................................................................................................... 11 Oil and Gas Operations .............................................................................................................................................. 12 Shoreline Debris ......................................................................................................................................................... 13 Grazing ..................................................................................................................................................................... 14 Wind Energy .............................................................................................................................................................. 14 Geologic Features and Processes ................................................................................ 19 Wind Activity ............................................................................................................................................................. 19 Wave and Current Activity.......................................................................................................................................... 19 Tidal Activity .............................................................................................................................................................. 19 Barrier Island System .................................................................................................................................................. 20 Lagoon System .......................................................................................................................................................... 23 Evaporite, Fulgurite, and Oolite .................................................................................................................................. 23 Shells ......................................................................................................................................................................... 24 Map Unit Properties .................................................................................................... 29 Geologic History .......................................................................................................... 33 Glossary ........................................................................................................................ 37 Literature Cited ............................................................................................................ 39 Additional References ................................................................................................. 45 Appendix A: Overview of Digital Geologic Data ....................................................... 46 Attachment 1: Geologic Resources Inventory Products CD PAIS Geologic Resources Inventory Report iii List of Figures Figure 1. Map of Padre Island National Seashore .............................................................................................................. 3 Figure 2. Coastal vulnerability index ............................................................................................................................... 15 Figure 3. Blowing sand .................................................................................................................................................. 16 Figure 4. Vehicle impacts ............................................................................................................................................... 17 Figure 5. Oil and gas operations..................................................................................................................................... 17 Figure 6. Grasslands of Padre Island National