Geology Along Going-To-The-Sun Road, Glacier National Park, Montana

Route

Start point

St. Mary

End point

Lake McDonald

Roads (and Trails)

Going-to-the-Sun Road

Total distance

35.8 miles

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Geology

Summary

This guide to the geology along Going-to-the-Sun Road in Glacier National Park describes many of the major geologic features of the Park. It is directed toward the Park visitor with little no no background in geology. The guide begins with a short introduction to the science of geology and the geologic time scale, followed by a simplified geologic cross section through the Park from SW to NE. The bulk of the field guide is a 21-stop road log, keyed to numered octagonal signs along the road, which describes the geology along the road. A glossary of geologic terms and an appendix is included which contains a brief geologic history of Glacier National Park, explanations of rock colors and fossil algae (stromatolites), and descriptions of the Proterozoic rock formations that can be seen along the Going-to-the-Sun Road. An extremely useful resource included at the back of the book is a fold-out geologic map, plotted on an oblique shaded-relief diagram, that depicts the landscape and the distribution of rock formations and faults in the vicinity of Going-to-the-Sun Road.

Key Lithologic Features

• Proterozoic sedimentary rocks of the Belt Supergroup
• Altyn Formation (limestone and dolomite)
• Appekunny Formation (mudstone and siltstone)
• Grinnell Formation (dolomitic siltstone, mudstone, and quartzite)
• Empire Formation (mudstone, siltstone, and quartzite)
• Helena (Siyeh) Formation (dolomite and limestone)
• Snowslip Formation (mudstone, siltstone,and quartzite)
• Shepard Formation (dolomitic siltstone, dolomite, and quartzite)
• Late Proterozoic igneous rocks (Purcell sill)
• Cretaceous shales
• Tertiary sedimentary rocks (Kishenen Formation)

Structures

• Lewis thrust fault

Landforms

• glaciated alpine terrain

Other Features

• stromatolites (fossil algae)

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Reference

Raup, O.B., Earhart, R.L., Whipple, J.W., and Carrara, P.E., 1983, Geology along Going-to-the-Sun Road, Glacier National Park, Montana : West Glacier, Montana, Glacier National History Association, 62 p.

Availability

Out of print. Check Amazon.com.