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🚙 Located  4.1   miles up the canyon from the intersection of Colorado Bvd. and US 14A at Spearfish GPS Coordinates N 44.26.253   W 103.52.379    4,048 ft.
Site Access
This lesson site is located along a parking turnout situated along the outer edge of a broad curve in the highway. The site is adjacent to a water control structure on Spearfish Creek which will be obvious. At this site we want to observe two geologic formations that are visible in the roadcut a short walking distance near the southern end of the parking turnout (see picture below). A short scramble up a moderately-steep slope of loose, rocky rubble is required if you feel compelled to actually observe the featured "contact" up close, but it can also be viewed satisfactorily from road level. Exercise extreme caution along the roadway.
Lavender Limestone Update 3.pdfIn–Depth Geology Lesson pdf
A great document to print for those who want to dig deeper into the geologic story.Â
The purple hue of ancient rockÂ
Is vivid as can be.Â
And hints of changes happening
Within the ancient sea.Â
Field Exploration
Field Exploration
Something unusual was occurring in the sea 360 million years ago as evidenced in our featured rock formation. In this self-guided exploration you'll be examining the transitional boundary between two great geologic formations and contemplating the subtle yet significant changes that were taking place in the ancient ocean. We promise you won't be disappointed!
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
The formational contact between the Lavender Englewood Formation and lighter Pahasapa Formation as seen at the lesson site just south of the parking area. See the Stratigraphic Column on the right for the position of the Englewood and Pahasapa Formations within the stack of rock layers exposed here in Spearfish Canyon.
The formational contact between the Lavender Englewood Formation and lighter Pahasapa Formation as seen at the lesson site just south of the parking area. See the Stratigraphic Column on the right for the position of the Englewood and Pahasapa Formations within the stack of rock layers exposed here in Spearfish Canyon.
Englewood                                                       Pahasapa
Englewood                                                       Pahasapa
Sitting just at the base of the Pahasapa,  the Englewood Formation is one of the thinner rock units in the canyon. Age and thickness are approximates.
Engelwood / Pahasapa Contact
Engelwood / Pahasapa Contact
These two formations formed in a shallow sea. The lower Englewood Formation formed during the transition from Devonian to Mississippian Time while the upper Pahasapa Limestone formed entirely within the Mississippian.Â
This picture displays a more defined contact not far from the study location. We did not include it in our lesson of study because of its unsafe proximity to the highway.
Formation Contact
Formation Contact
The Englewood / Pahasapa contact is sometimes obvious in the surrounding cliffs due to the contrast in formational colors. The Englewood is the lower, brightly-colored formation.
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
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