Field Trips in the area

Study all you want to. But until you get out in the field, the classroom or textbook is paper and pictures. If you want to understand structural geology, only seeing what geological forces did to change what was once a massive series of horizontally deposited material into anticlines, synclines and faults will do. Bending them over and tilting them upwards they form large structural forms best observed from the field.

The added benefit from taking a field trip is you get plenty of fresh air and exercise.

These are not "roadside geology" examples. You need to drive and get out and walk!

Here are some pictures from two sites.

Sandy Hollow  

The first is accessed from highway 41 (head towards Dillon from Twin Bridges) and go to the Pennington Bridge Notch Bottom fishing access sign. Head West approximately 10.5 miles until you see and access road on the North side of the road (if you get to the Notch bottom fishing access you have gone too far).

Please respect this site as it is used by most of the field camps in the area. You know you are on top of the anticline when you reach GPS N47 34.993 W122 28.900. This formation is known as the Sandy Hollow formation. A good description can be found from Sears et al, 1989 (TRGS meeting - Northwest Geology volume 18)

Bannack Mining District 

The second site is by Bannack, MT. You may just want to wander around to find good sites. However if you take the road above Bannack and continue approximately 2 miles you should see plenty of the lower Beaverhead formation.  GPS N112.96927 W45.14642. These appear to be clastic in nature and probably traveled short distances in developing the fans. They are surrounded by paleosoils.  The full field trip can be found by reading Larry Johnson "A field Guide to the stratigraphy, structure and mining history of the Bannack area", Montana p 245-249 Dillon Filed Conference North west Geology Volume 36, August 2007

Field guides and more information can be found at the  Tobacco Root Geological Society http://trgs.org/ web site.

Notch Bottom Sandy Hollow

Sandy Hollow Anticline

Gastropod Formation (fossil is approx. 4mm)

Anticline just north of the Sandy Hollow duplex

Bannack Mining District

Upper Beaverhead Clastic deposits surrounded by paleosoils

Clastic characterisitics of the Beaverhead formation

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