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“Bite-Size Bits of Local, National, and Global History”
“Bite-Size Bits of Local, National, and Global History”
Paradise in Sanders County, Montana — The American West (Mountains)
 

Phantom Formation Is Rock Solid In Corridor

Clark Fork Corridor: The Land

 
 
Phantom Formation Is Rock Solid In Corridor Marker image. Click for full size.
By Bernard Fisher, July 22, 2011
1. Phantom Formation Is Rock Solid In Corridor Marker
Inscription. Imagine a rock so old and so deep, that in some places, the bottom has never been found! The mountains you have been driving through are made up of such a rock—the Prichard Formation. Dating back 1.5 billion years, it is one of the oldest exposed sedimentary rocks in western Montana. The Prichard is over 4 miles thick at the confluence of the Clark Fork and Flathead rivers and its base has yet to be discovered.

Across the river, the uplifting and shifting of the mountains has tilted the Prichard on its side. If you look closely at the large rocks at this turnoff, you may see ripple marks and mud cracks—evidence of their sedimentary origin.

Rock of Many Uses
Because the mudstone layers in the Prichard split apart to form flagstone, it has been quarried to provide colorful construction material for hearths, stone paths and facings for buildings. In addition, a slate-like rock found in the formation was used by early people to make tools and weapons.

Ancient Origins
The Prichard formed as layer upon layer of sand, silt and clay was deposited from a river delta into a sea covering parts of what is now Montana, Idaho, Washington and Canada. Over millions of years, heat and pressure turned the sediments into a hard, metamorphic rock, argillite.
 
Erected by
Exposed sedimentary rock of the Prichard Formation image. Click for full size.
By Bernard Fisher, July 22, 2011
2. Exposed sedimentary rock of the Prichard Formation
Lolo National Forest.
 
Location. 47° 19.053′ N, 114° 48.275′ W. Marker is in Paradise, Montana, in Sanders County. Marker is on State Highway 135 3.3 miles south of State Highway 200, on the right when traveling south. Click for map. Marker is in this post office area: Paradise MT 59856, United States of America.
 
Other nearby markers. At least 5 other markers are within 2 miles of this marker, measured as the crow flies. Native People Sustained Through Many Millennia (a few steps from this marker); The Earth's Blood Flows Past You (a few steps from this marker); Coursing Through Miles Of Montana (approx. 1.9 miles away); Searching For Fur And A Finer Life (approx. 1.9 miles away); Wildlife Thrive In Corridor Year Round (approx. 1.9 miles away).
 
Also see . . .  Lolo National Forest. (Submitted on July 29, 2011, by Bernard Fisher of Mechanicsville, Virginia.)
 
Categories. Natural Features
 
The Clark Fork (facing north) image. Click for full size.
By Bernard Fisher, July 22, 2011
3. The Clark Fork (facing north)
 
 
Credits. This page originally submitted on , by Bernard Fisher of Mechanicsville, Virginia. This page has been viewed 567 times since then and 21 times this year. Photos:   1, 2, 3. submitted on , by Bernard Fisher of Mechanicsville, Virginia. This page was last revised on June 16, 2016.
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