Barker Mountain Geology Field Trip and Hike

Sunday, July 15, 2007

Barker Mountain is the prominent peak on the skyline of the Little Belt Mountains when traveling from Great Falls towards Belt on U.S. Highway 89.  In the photo above Wolf Butte is the sharp peak on the far left and Big Baldy, the highest peak in the Little Belts, is the snow-covered peak on the distant skyline just to the right of Barker Mountain.  All of these peaks are igneous intrusions, known as laccoliths..

• Location -- This is an introductory level field trip and hike to look at natural features in the Little Belt Mountains, located about 60 miles southeast of Great Falls, Montana, U.S.A. Take U.S. Highway 89 to the meeting place at the Cub's Den, located in Monarch.  Flora, fauna, and geology of the area will be discussed on the hike.



• The Hike -- We will drive to Kibbey Divide above Hughesville, and hike to the top of Barker Mountain and back   In the 3-fold ranking of difficulty--easy, moderate, and strenous--this hike is rated as moderate.  Middle-School students can do it; and active and fit Seniors in their 70's can do it.  The route follows the large ridge shown in the right half of the photo below, climbing about 1750 feet in elevation over a distance of about 2 miles.  Bring your camera.  There will be great views of the Highwood Mountains and other features.
  
  
• Geology of the Barker/Hughesville Area -- Hughesville is at the center of a cluster of igneous intrusions.  The small Hughesville Stock is surrounded by three laccoliths.  These are the Barker Laccolith, shown in the photo below, the Clendennin Mountain/Peterson Mountain Laccolith, and the Mixes Baldy/Anderson Peak Laccolith.  The largest body of lead/zinc/silver ore is located in the Hughesville Stock.  The age of the igneous rocks is about 50 million years.




Barker Mountain as seen from Clendennin Mountain.



• Ore Deposits -- The Barker/Hughesville Mining District is a classic lead/zinc/silver locality.  There are many smaller deposits at the contact between the igneous rock--porphory--and limestone.  The largest ore body is at the Block P Mine.  It has the shape of an inverted cone within the Hughesville Stock.  The major ore minerals are galena (=lead sulfide), sphalerite (=zinc sulfide), and pyrite (=iron sulfide).
  
  
• Reclamation -- The Barker/Hughesville Mining District is a Superfund site.  Reclamation of the tailings pond at Barker has been completed.  Other work is ongoing.
  
  
• Scenic Views -- The photo below shows the view from Kibbey Divide, the starting point of the hike.  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 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.




View from Kibbey Divide looking north down into Big Otter Creek.  The Highwood Mountains on the far skyline consist of a stack of lava flows on top of Cretaceous-age sedimentary rocks.  The lava flows are covered with forest whereas the sedimentary rocks below lack forest cover.  The prominent cliff of Madison Limestone in the center of the photo dips 30° to the left due to the forceful igneous intrusion--the Clendennin-Peterson Laccolith--inside of Clendennin Mountain (on the right side of the photo).   Limestone Butte is on the skyline on the left side of the photo, covered with dense forest.  A laccolith inside the butte has bulged up the sedimentary rocks, including the Madison Limestone on the surface, to make a dome.



• Flora and Fauna of the Barker/Hughesville Area -- Lists of the mammals, birds, and plants found in Paine Gulch, the valley to the south of Dry Fork, 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 -- Dr. David Baker, Earth Scientist in Monarch, and Wayne Green, Hydrologist, will lead the hike.




• 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) 236-5934 or (406) 727-2240 or fill out our on-line registration form. Meeting time is 8:00 a.m.

  Geology Field Trips and Hikes  Central Montana Geology  Monarch Area  Contact Us