Road Log from Bozeman to Specimen Creek via Gallatin Canyon and U.S. 191

Route

Start point

Bozeman, Montana

End point

Specimen Creek Trailhead

Roads

U.S. 191, Gooch Hill Road

Total distance

61.7 miles

---

Geology

Summary

This trip leads southward through the Gallatin Range to Specimen Creek in Yellowstone National Park. It affords an excellent worm's-eye view of the structure and stratigraphy of this range as revealed both laterally and vertically through the quietly beautiful Gallatin Canyon. The route also borders the east margin of the Madison Range and its spectacular Spanish Peaks uplift. The Gallatin and Madison Ranges are geologically and topographically similar, an essential difference being the thick cap of andesitic lava and breccia that covers the high parts of the Gallatin Range.

Key Lithologic Features

• alluvial fans in the Bozeman area
• Archean gneisses and pegmatites in Gallatin Canyon
• Paleozoic sedimentary rocks
• andesite porphyry sills
• glaciall and ancient lake deposits in Gallatin Canyon
• Black Butte andesite porphyry stock and Gallatin River laccolith
• Huckleberry Ridge Tuff
• landslide and mudflow deposits

Structures

• range front flexure along the north side of the Gallatin Range
• Squaw Creek reverse fault

Landforms

• Gallatin Canyon
• Gallatin River
• Stormcastle Mountain
• Garnet Mountain

Other Features

• Yellowstone National Park (NW corner)

---

Reference

Montagne, J.M., and Chadwick, R.A., 1976, Road Log from Bozeman to Specimen Creek via Gallatin Canyon and U.S. 191, in Lankston, M.M., ed., Guidebook (of selected areas in southwestern Montana) ; from the 1st Annual Tobacco Root Geological Society Field Conference, Bozeman, MT, Montana Bureau of Mines and Geology Special Publication 73, p. 37-52.

Availability

Order from the Tobacco Root Geological Society c/o the Montana Bureau of Mines and Geology. Go to the TRGS publications page for ordering information.