| In western Millard County, Utah, near the eastern boundary with White Pine County, Nevada, a classic geologic section exposes three Paleozoic Era rock formations: Ledge and level area at bottom to upper middle, above person with hat, is the middle to late Devonian Guilmette Formation--a noted producer of corals, stromatoporoids (extinct calcareous sponge), gastropods, brachiopods, crinoids, ostracods, and conodonts; lighter-colored pale brown rocks, above the Guilmette, belong to the late Devonian to lower Mississippian Pilot Shale (contains many species of conodonts); and the massive darker colored strata, to the skyline, correspond to the middle Mississippian Joana Limestone (yields locally abundant corals, brachiopods and crinoids, in particular). Photograph courtesy Harry E. Cook and James M. Corboy; I edited and processed the image through photoshop. |