(CN) – The dense collection of Jurassic dinosaur fossils at the Cleveland-Lloyd Dinosaur Quarry has been the subject of several theories that seek to explain how and when it originally formed. Did the dinosaurs there die from drought? Were they stuck in thick mud?
A study published Tuesday in the journal PeerJ uses modern techniques to determine the site’s history, finding the quarry includes several death cycles that brought the dinosaurs to the site over time, as opposed to a single event.
“The quarry is world-famous for its unusually high concentration of dinosaur bones,” the study says. “Since the initial discovery of the site in 1927, nearly 10,000 bones have been collected by at least seven institutions.”
The new study reveals that the small bone fragments at the quarry were created during drought periods that weathered and eroded bones that were disintegrating at the surface. During flood periods, on the other hand, the carcasses of Allosaurus and other dinosaurs washed in and rotted in a small pond, forming an environment in which turtles, fish and crocodiles could not survive. Other dinosaurs would not eat the carcasses.
Using chemical analyses and studying microscopic bone fragments, the team found that the dinosaur bones were introduced to the quarry after death. This discovery could also explain the unusual lack of typical pond fossils at the site, as well as the few examples of gnaw marks on bones and calcite and barite concretions found on bones excavated from the quarry.
The new theory can help paleontologists understand the setting of the quarry, and begin to unravel the mystery that led to the creation of the unique bone bed.