National Park Service U.S. Department of the Interior Geologic Resources Division Denver, Colorado Glacier National Park Geologic Resource Evaluation Report Glacier National Park Geologic Resource Evaluation Geologic Resources Division Denver, Colorado U.S. Department of the Interior Washington, DC Table of Contents List of Figures .............................................................................................................. iv Executive Summary ...................................................................................................... 1 Introduction ................................................................................................................... 3 Purpose of the Geologic Resource Evaluation Program ............................................................................................3 Geologic Setting .........................................................................................................................................................3 Glacial Setting ............................................................................................................................................................4 Geologic Issues............................................................................................................. 9 Economic Resources..................................................................................................................................................9 Mining Issues..............................................................................................................................................................9 Avalanche Hazards ..................................................................................................................................................10 Wetlands ..................................................................................................................................................................10 Cave Resource Issues .............................................................................................................................................10 Seismicity .................................................................................................................................................................11 Slope Processes.......................................................................................................................................................11 Glacier Formation .....................................................................................................................................................12 Paleontologic Potential .............................................................................................................................................12 Faulting and Deformation Processes........................................................................................................................12 Glacial Retreat..........................................................................................................................................................13 Water Issues.............................................................................................................................................................13 Streamflow, Channel Morphology and Sediment Load.............................................................................................14 Wind Erosion and Deposition ...................................................................................................................................14 General Geology ......................................................................................................................................................14 Geologic Features and Processes............................................................................. 16 Glacial Features .......................................................................................................................................................16 Glacial Retreat..........................................................................................................................................................17 Glaciers ....................................................................................................................................................................18 Short-lived Glacial Features .....................................................................................................................................18 The Belt Supergroup ................................................................................................................................................18 Faults at Glacier .......................................................................................................................................................19 Akamina Syncline .....................................................................................................................................................20 Formation Properties.................................................................................................. 29 Formation Properties Table ......................................................................................................................................20 Geologic History.......................................................................................................... 33 References................................................................................................................... 44 Appendix A: Geologic Map Graphic .......................................................................... 48 Appendix B: Scoping Summary................................................................................. 49 Appendix C: Geoindicators Scoping Report ............................................................ 52 Attachment 1: Digital Geologic Map (CD) GLAC Geologic Resource Evaluation Report iii List of Figures Figure 1: Map of Montana with physiographic features surrounding Glacier National Park ...........................................6 Figure 2: Map of structural features in Glacier National Park area.................................................................................7 Figure 3: Map showing location of Glacier National Park in relation to Pinedale glacier and ice sheets........................8 Figure 4: Photo of three hanging valleys......................................................................................................................21 Figure 5: Diagrammatic view of a retreating glacier .....................................................................................................22 Figure 6: Map of Glacier National Park showing locations of the largest glaciers present today .................................23 Figure 7: The aerial extent of Sperry Glacier ...............................................................................................................24 Figure 8: Short-lived surface features on glaciers........................................................................................................24 Figure 9: Formation of stromatolites.............................................................................................................................25 Figure 10: Location of Glacier National Park relative to the entire Belt Terrane...........................................................26 Figure 11: Structural features east of Glacier National Park ........................................................................................27 Figure 12: Prominent structural features inside Glacier National Park .........................................................................28 Figure 13: Map of present day structural features superimposed on preexisting features ...........................................37 Figure 14: Depositional environment of the Prichard-Altyn Formation .........................................................................38 Figure 15: Conceptual depositional environment of the Ravalli Group.........................................................................38 Figure 16: Middle Belt Carbonate depositional facies ..................................................................................................39 Figure 17: Conceptual depositional environment of the Missoula Group .....................................................................40 Figure 18: Inferred Proterozoic structure of the Belt basin during Missoula Group deposition.....................................41 Figure 19: Subaqueous and subaerial phases of Purcell Lava ....................................................................................41 Figure 20: Deposition of the Kishenehn Formation ......................................................................................................42 Figure 21: Geologic Time Scale...................................................................................................................................43 iv NPS Geologic Resources Division Executive Summary This report has been developed to accompany the digital geologic map produced by Geologic Resource Evaluation staff for Glacier National Park in Montana. It contains information relevant to resource management and scientific research. The story of Glacier National Park is the story of geology • Glacial retreat. The park was created to preserve and and ice: the