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🚙 US-14A Mileage 1.2          GPS Coordinates  N44.28.044 W103.15.072    3,762 ft.
Echoes of Coastal Desert Update2.pdfLesson Guide: PRINT
An ancient desert by the seaÂ
Where sands drift freely by
Then turn to stone in layered styleÂ
Beneath the clear blue sky
Field Exploration
Field Exploration
Are you ready for a trip back in time? During this exploration we'll take you on a short hike down the rocky Spearfish creek-bed to the ancient shoreline of a warm, salty sea – one that occupied this region of the continent eons ago. You won't get wet but you will be inspired!
This pdf Lesson Guide contains the specific directions for reaching our featured site as well as a detailed explanation of its geologic story. Mileage and coordinates are provided in each document and roadmaps and other learning aids can be found at the Lesson Resources link in the sidebar menu. The document is most useful if taken with you to the lesson site. Exercise extreme caution at the lesson site and along roadways.
Are you ready. . . . Let's Go!                        S. V. Fogarty  &  W. R. Stevens
*Mileage starts at the intersection Colorado Bvd. and US 14A near Spearfish.
The trail to the lesson site begins just to the right of the kiosk and leads to Spearfish Creek.
The trail to the lesson site begins just to the right of the kiosk and leads to Spearfish Creek.
Once you've reached Spearfish Creek, follow the stream bed to your right (NE) for about 100 yards.
Once you've reached Spearfish Creek, follow the stream bed to your right (NE) for about 100 yards.
DO NOT attempt to access this site when it's raining or during the spring melt. As you can see from the size of the riverbed cobbles the stream flow can be quite high during such events.
Sitting atop the Pahasapa Limestone, the Minnelusa Formation is one of the thicker rock units in the canyon. Age and thickness are approximates.
This lesson features the Minnelusa Sandstone which is exposed along north side of stream bed. The Minnelusa Formation was deposited during Pennsylvanian and Permian Time some 300 to 250 million years ago. Because this is a marine deposit we know that at the time of its deposition the Black Hill's, as an uplifted mountain range, did not exist. Note the thickness and position of the Minnelusa Formation in the stratigraphic column to the left.Â
This lesson features the Minnelusa Sandstone which is exposed along north side of stream bed. The Minnelusa Formation was deposited during Pennsylvanian and Permian Time some 300 to 250 million years ago. Because this is a marine deposit we know that at the time of its deposition the Black Hill's, as an uplifted mountain range, did not exist. Note the thickness and position of the Minnelusa Formation in the stratigraphic column to the left.Â
Sandy sediments, when deposited in the ocean, generally accumulate layer-by-layer close to the shoreline. In this outcrop we can clearly see those thin stratifications of sand which over the eons eventually lithified (hardened) into sandstone.
Sandy sediments, when deposited in the ocean, generally accumulate layer-by-layer close to the shoreline. In this outcrop we can clearly see those thin stratifications of sand which over the eons eventually lithified (hardened) into sandstone.
Be sure to download our Onsite Geology Lesson PDF posted above for a detailed geologic investigation of this site.Â
Send comments to: partial.melting@gmail.com
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