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| The park exhibit sign next to a limestone outcrop says, "PAHA SAPA LIMESTONE -- All Black Hills caves have formed in this layer 300 to 600 feet thick. Originally it was laid down on a shallow seabottom about 300 million years ago. Its name derives from the Lakota word meaning 'Black Hills'." An artificial entrance to the cavern is to the right along the trail. The Pahasapa Limestone (also known regionally as Madison Limestone) is Mississippian age (between 318 and 360 million years) and crops out in a belt around the uplifted core of the Black Hills (NPS, 2009). |
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