Phantom Formation Is Solid Rock In Corridor- Paradise, MT
Posted by: Groundspeak Premium Member T0SHEA
N 47° 19.050 W 114° 48.281
11T E 665905 N 5242784
This is the third of three historical markers on the Clark Fork River along Highway 135, 6 miles south of Paradise, Montana. It is entitled Clark Fork Corridor: The Land.
Waymark Code: WMMWW4
Location: Montana, United States
Date Posted: 11/16/2014
Published By:Groundspeak Premium Member muddawber
Views: 1

PHANTOM FORMATION IS ROCK SOLID IN CORRIDOR
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.
From the marker
Describe the area and history:
The river, the Clark Fork, is directly in front of the reader. The rest of the natural world spreads out behind it. The mountains described rise both behind and in front of the viewer.


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