Paine Gulch Geology Field Trip and Hike

August 27, 2005

• Location -- This is a geology field trip and hike to look at features in the Little Belt Mountains, located about 45 miles southeast of Great Falls, Montana, U.S.A. Take U.S. Highway 89 to the meeting place at the Lazy Doe Bar & Restaurant, located about 1½ miles south of Monarch.



• The Hike -- The hike goes up the bottom of Paine Gulch to the end of the second meadow--the long light green patch in the bottom of the gulch in the photo above--and then climbs to the crest of Dry Ridge (with the prominent cliff) on the left.  The return route follows the crest of the ridge to where the photo was taken and then descends to the highway.



• Forest Fire in Paine Gulch -- Paine Gulch is a designated Research Natural Area in the Lewis & Clark National Forest.  As can be seen in the photo, a forest fire in 2001 burned over 50% of the gulch.  The left side of the gulch faces south and is warmer and dryer than the right side in the photo.  Most of the fire was on the left side--predominately Ponderosa pine--rather than the right side which is covered with lodgepole pine.  On the afternoon of September 4, 2001 there was a wall of flames 100 to 200 feet high extending from the bottom of the gulch to the top of Dry Ridge on the left.  The wall of flames advanced at a steady rate down the gulch.  The fire was extinguished by a snowstorm.






• Geology of Paine Gulch -- Paine Gulch is carved into sedimentary rocks of Lower Paleozoic age (330 to 550 million years old) that are tilted about 7° north towards Great Falls.  Cambrian age formations (limestone and shale can be found near the mouth of the gulch.  The Devonian age Jefferson Dolomite forms prominent cliffs above the lower end of the gulch and forms the "band" halfway up the left slope in the photo above.  The hiker in the photo is resting on Madison Limestone of Mississippian age, which forms the upper part of both Dry Ridge on the left and Sun Mountain on the right.  The limestone and dolomite are good aquifers (and also contain abundant fossils). Nearly all the rainfall in Paine Gulch (which does not evaporate or is not transpired by the forest) disappears into the ground and flows underground to Giant Springs.  This is part of the recharge area for the Madison Limestone Aquifer.



• Flash Floods in Paine Gulch -- Paine Gulch is always dry except after a major forest fire.  In the Summer of 2002 with more than half the forest cover removed by the 2001 fire, thunder storms quickly created flash floods.  There were 5 flash floods in 6 weeks, each with about a million cubic feet of water that roared down the gulch.  No flash floods have occurred since because of the speed with which the plant cover was regenerated.  The gulch is about a thousand feet deep, carved by flash floods that run for a year or so after major forest fires.



• Scenic Views -- From the top of Dry Ridge hikers will be able to see many prominent peaks formed by igneous intrusions--laccoliths. Thunder Mountain, Tiger Butte, and Tillinghast Mountain are laccoliths to the west of Belt Creek. The Barker laccolith, the Clendennin/Peterson Mountain laccolith and the Mixes Baldy/Anderson Peak laccolith are near Hughesville/Barker. The highest peak in the Little Belt Mountains is formed by the Big Baldy laccolith. Long Mountain and Neihart Baldy are prominent peaks because they are capped by the very resistant Neihart quartzite and are uplifted as part of the Pioneer Ridge Uplift--a block of basement 8 miles long by 6 miles wide that was uplifted about one and half miles vertically.






• Flora and Fauna of Paine Gulch -- Lists of the mammals, birds, and plants found in Paine Gulch are available on the internet. Both the common names and the scientific names are listed. To see photos of these plants and animals, use the Image Search Engine at Google and search for the common name or the genus and species.



• Field Trip Leaders -- Al Koss, District Ranger, will lead the hike. Dr. David Baker, Earth Scientist in Monarch, will comment on the geology and other natural features.



• Registration and Cost -- There is no charge for the field trip; however, prior registration is required. The group size is limited. To register, call (406) 236-5511 or fill out our on-line registration form. Meeting time is 9:30 a.m.

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