Lavender Limestone: The Englewood Formation

🚙  US-14A Mileage 4.1                                                     GPS Coordinates  N 44.26.253     W 103.52.379        4,048 ft.

Lavender Limestone Update2.pdf

Lesson Guide: PRINT

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 document contains the specific directions for reaching our featured Lesson Site as well as a detailed explanation of its geologic story. Mileage to the site as well as its specific coordinates are listed on the header above and also in the lesson document. Roadmaps and other learning aids can be found at the Lesson Resources link in the menu and are helpful to have handy in the field. Please print this document and take it with you or read it thoroughly before departing. 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.

Spearfish Stratigraphic Column

Note the position of the Englewood Formation. Age and thickness of geologic formations are approximate.

Englewood / Pahasapa Formation contact.

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.

Comparison of Englewood and Pahasapa rock samples.

Englewood                                                        Pahasapa

Englewood (lower) / Pahasapa (upper) Formation contact.
Englewood Englewood (lower) / Pahasapa (upper) Formation 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. 

The lower 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.

The Englewood / Pahasapa contact is sometimes obvious in the surrounding cliffs due to their highly contrasting colors.

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.


Be sure to download our Onsite Geology Lesson PDF posted above for a detailed geologic investigation of this site. 


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