Hell Creek Formation
The Turtle Graveyard is the worlds most important fossil turtle site. It is a very rich site where we have uncovered over 75 baenid turtle shells, many baenid skulls and postcranial material, as well as partial skeletons of plastomenid turtles and flat rays. The MRF director, Tyler Lyson, has been collecting this site for 9 years and is currently describing two new taxa found at the locality. The site has also yielded material from Trionychid turtle shells and skulls, some crocodile material, and a few therapod bones. The Turtle Graveyard is a favorite among volunteers because of its close proximity to a road (about 15 meters), soft sandy matrix, and most importantly, the shade tarp that is put up every year!
The sedimentology, close association, but differential preservation of the skeletons, and number of large logs found at the site indicates a taphonomic history in which pool of standing water or slow moving stream dried up during a drought, killing the trapped turtles and rays. The turtles were subsequently buried during a debris-type flow such as a high velocity flood event.