Badlands National Park scenic. The landscape of the South Dakota Badlands are made up of highly eroded layers of sedimentary rock formed from layers of mud deposited between 34 and 77 milion years ago when the regions climate was much wetter. The layers are composed of tiny grains of sediments such as sand, silt, and clay that have been cemented together into sedimentary rocks. Slowly, over time the climate became dryer and these layers were eroded into the landscape we now see. These soils are among the richest Oligocene fossil beds known to exist. Remains of three-toed horses, dog-size camels, saber-toothed cats, giant pigs, and other species have been found here; all date from 28 million to 37 million years ago.