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

Madison Limestone and the Garnet Mountains

 
 
Madison Limestone and the Garnet Mountains Marker image. Click for full size.
By Duane Hall, August 8, 2010
1. Madison Limestone and the Garnet Mountains Marker
Inscription. About 350 million years ago, much of Montana was submerged under a shallow sea. Billions of tiny marine creatures thrived in the water and when they died their bodies settled into the muck on the sea bed. After hundreds of millions of years of accumulation and many more millions of years it metamorphosed into the pale gray rocks that known today as Madison Limestone. The limestone is common throughout Montana, eastern Idaho, northern Wyoming, and in the Dakotas. In Montana, the limestone beds are from 1,000 to 2,000 feet thick in places. Because Madison Limestone resists weathering and erosion much better than most other kinds of rocks, it forms many of the spectacular cliffs and dramatic ridges that make Montana such a scenic place to drive through. A magnificent outcrop of Madison Limestone is visible on the north side of Interstate 90 just a few miles east of this rest area. The limestone pinnacles were exposed when the soil around them eroded away, creating the dramatic canyon along the Clark Fork River. The red streaks visible on the rocks and soil is iron oxide.

About 75 million years ago molten rock intruded the area near the crest of the Garnet Range, seven miles north of this rest area. Northwest-trending faults and rock layers channeled mineral-rich fluids from the intrusion into Cambrian and Precambrian rocks to
Close-up of Garnet Mining Area Map on Marker image. Click for full size.
By Duane Hall, August 8, 2010
2. Close-up of Garnet Mining Area Map on Marker
form three principal gold veins and numerous smaller, gold-bearing zones. Prospectors discovered gold placers at the mouth of Bear Gulch, about a mile northeast of the rest area in 1865; discoveries in other drainages of the Garnet Range soon followed. Although gold-bearing veins were discovered in 1866, the technology was not readily available to work them. By 1896, however, numerous underground mines were producing gold, silver, and copper. In 1898, more than 1,000 people lived in the town of Garnet to support the miners living in the surrounding area.


Geo-Facts:
Geo-Activity:
 
Erected by Montana Department of Transportation.
 
Location. 46° 43.154′ N, 113° 18.748′ W. Marker is near Drummond, Montana, in Granite County. Marker is on I-90 Frontage Road 1.1 miles east of Bear Gulch Road, on the right when traveling west. Touch for map. This marker is not located at the I-90 Bearmouth Westbound Rest Area, but is located on the I-90 Frontage Road which can be accessed from I-90 at Exit 138 and Exit 153 (Drummond). Marker is in this post office area: Drummond MT 59832, United States of America.
 
Other nearby markers. At least 2 other markers are within 9 miles of this marker, measured as the crow flies. Rattler Gulch Limestone Cliffs ACEC (approx. 3.9 miles away); Sand Park Cemetery (approx. 8.6 miles away).
 
More about this marker. There is an identical marker located at the I-90 Bearmouth Eastbound Rest Area. The references to rest area in the marker text inscription are to this rest area which is located west of the Madison Limestone outcropping and this marker.
 
Categories. EnvironmentIndustry & CommerceSettlements & Settlers
 
 
Credits. This page was last revised on June 16, 2016. This page originally submitted on January 28, 2014, by Duane Hall of Abilene, Texas. This page has been viewed 426 times since then and 43 times this year. Photos:   1, 2, 3. submitted on January 28, 2014, by Duane Hall of Abilene, Texas.
 
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