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🚙 Located 0.9 miles up the canyon from the intersection of Colorado Bvd. and US 14A at Spearfish          GPS Coordinates N 44.28.242   W 103.50.941     3,758 ft.
Site Access
This investigation centers around a small outcrop of the Minnelusa Formation exposed in a hillside directly along the highway. The outcrop will be on your left side when driving up the canyon from Spearfish but, given its orientation and a camouflage of vegetation, it’s not readily visible when driving this direction. Because of this we suggest you first do a “drive-by" and then turn around at the Spearfish Canyon Informative Kiosk parking area located 0.3 miles ahead on the right. Once you’ve turned around and are headed north, the outcrop will be more readily apparent and you’ll be able to park directly alongside which is the safest parking option. Remember to turn on your flashers when parked.
Artisan Earth Update 3.pdfIn–Depth Geology Lesson pdf
A great document to print for those who want to dig deeper into the geologic story.Â
A delta forms along the shoreÂ
From sands entrained in flow.
That settle out in cross-bed formsÂ
Like artwork in a show.
Field Exploration
Field Exploration
Is it possible for an outcropping of rock be classified as a work of art? We think so, and in this exploration we'll introduce you to the ancient Minnelusa Sandstone, a formation whose unique appearance may just qualify it for a blue ribbon. At this site you'll view one of the canyon's most stunning rock-faces and learn about the geologic processes that brought it to be!Â
This pdf Lesson Guide contains the specific directions for reaching our featured site as well as a detailed explanation of its geologic story for those desiring more depth. Mileage and coordinates are provided in each document and roadmaps and other learning aids can be found at the Geologic Resources link in the sidebar menu. The document is most useful if you have it in hand at the geologic site. Exercise extreme caution at the lesson site and along roadways.
Are you ready. . . . Let's Go!                        S. V. Fogarty  &  W. R. Stevens
Minnelusa Outcrop along the east side of Highway 14A a short distance from the Spearfish Canyon Informational Kiosk and parking area. When driving up the canyon from the town of Spearfish, it's quite easy to miss the outcrop due its south-facing orientation. Please pay close attention to the traffic when looking for the outcrop and use caution along highway.
The roadside outcrop of the Minnelusa Formation is both spectacular and curious in its appearance. The depositional qualities of the Minnelusa sediments, along with their selective response to Weathering, has resulted in an exposure dominated by a myriad of eye-catching erosional textures. The Minnelusa is a shallow marine sediment laid down during Pennsylvanian and Permian Time some 300 to 250 million years ago. See the Stratigraphic Column below for the position of the Minnelusa Sandstone within the formations exposed here in Spearfish Canyon.
The roadside outcrop of the Minnelusa Formation is both spectacular and curious in its appearance. The depositional qualities of the Minnelusa sediments, along with their selective response to Weathering, has resulted in an exposure dominated by a myriad of eye-catching erosional textures. The Minnelusa is a shallow marine sediment laid down during Pennsylvanian and Permian Time some 300 to 250 million years ago. See the Stratigraphic Column below for the position of the Minnelusa Sandstone within the formations exposed here in Spearfish Canyon.
Alternating hard and soft layers create the beautiful ribbed texture. Magnified view from picture above.
Alternating hard and soft layers create the beautiful ribbed texture. Magnified view from picture above.
Honeycomb Weathering is sometimes referred to as Tafoni. Magnified view from picture above.
Honeycomb Weathering is sometimes referred to as Tafoni. Magnified view from picture above.
There's more to this story than meets the eye. Download our In-Depth Lesson pdf above if you desire a more thorough coverage.Â
Send comments to: partial.melting@gmail.com
The Minnelusa Formation contains some of the widest variety and most interesting sedimentary structures in the canyon. Â Age and thickness are approximates.
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