Photograph (left) and partially stained photomicrograph (right)

Photograph (left) and partially stained photomicrograph (right) of a layered phreatic speleothem from the lower passages of Wind Cave National Park, South Dakota. Photograph shows millimeter-scale subsamples analyzed for U-series disequilibrium dating plus ⁸⁷Sr/⁸⁶Sr, ²³⁴U/²³⁸U, δ¹⁸O, and δ¹³C analyses. (Photo credit: James Paces, Margaret Palmer)