Bands of Time

Bands of Time. . , Rock layers in Badlands National Park contain fossils that show a dramatic cooling and drying of global climate over millions of years. The oldest rock layers contain marine fossils, roughly 70 million years old, from when this area was underwater. Although dinosaurs lived during this time, they did not live in this area. Younger layers show evidence of cooler and drier climates. The most recent layers reveal animals and plants from an open shrubland. Today, rock layers are stripped away by erosion, exposing new fossils within these bands of time. , Sharps Formation , 28 to 30 million years ago , Sediments of the Sharps Formation preserve evidence of a cool and dry shrubland. , Rockyford Ash , 30 million years ago , This thick layer of volcanic ash forms the bottom layer of the Sharps formation. , Brule Formation , 30 to 34 million years ago , Open woodlands preserved In the Brule Formation were direr and cooler than those in the Chadron Formation. In some areas water was hard to find. , Chadron Formation , 34 to 37 million years ago Sediments carried by streams and rivers flowing from the Black Hills created this formation. These sediments were deposited in a hot and humid forest flood plain. , Yellow Mounds , 67 to 75 million years ago , After the sea drained away, the black ocean mud was exposed to surface weathering. The upper layers of this mud developed into a yellow soil called Yellow Mounds. , Pierre Shale , 67 to 75 million years ago , This formation first began to form 75 million years ago when a shallow sea covered this area. , Oreodont , Leptauchenia , 28 to 32 million years ago , Nimravid , Nimravus , 30 to 32 million years ago , Three-toed Horse , Mesohippus , 30 to 37 million years ago , Dog , Hesperocyon , 28 to 37 million years ago , Titanothere , Brontops , 34 to 37 million years ago , Alligator , Alligator , 34 to 37 million years ago , Ammonite , Placenticeras , 67 to 75 million years ago