New Explanation for Fossil-Rich Bone Bed

Just outside of Bakersfield, California lies a remarkable fossil bed that stretches over an area of 50 square miles. The site, known as Sharktooth Hill Bone Bed, was discovered in the 1850s and has yielded a surprising diversity of fossils—ancient seals, sea turtles, dolphins, whales and sharks. The bone deposits within Sharktooth Hill are so dense they form an earthen layer that varies in thickness from six to 20 inches.

Experts have long debated how such a concentrated collection of bones were preserved at this single location. One proposed explanation is that the Sharktooth Hill was a killing ground for megalodon, a 40-foot shark that roamed the seas around 15 million years ago. Another explanation suggests the site was a long-time breeding grounds for seals and other marine mammals.

Now, a team of paleontologists from University of California, Berkeley, the University of British Colombia, Vancouver, and the University of Utah have suggested yet another possible explanation for the bones at Sharktooth Hill. The researchers propose that the bone bed records a 700,000-year period between 15 and 16 million years ago when normal life and death cycles in the region were preserved under unusual climate conditions.

At the time Sharktooth Hill Bone Bed formed—between 15,900,000 and 15,200,000 years ago—California's Central Valley lay beneath an inland sea known as the Temblor Sea. Many of the bones collected from Sharktooth Hill were scattered as if they had been moved by water currents. As one scientist from the UC Berkeley team described:

"The bones look a bit rotten, as if they lay on the seafloor for a long time and were abraded by water with sand in it," ~ Jere Lipps, University of California, Berkeley.

The research team suggests that Sharktooth Hill formed during a period of 100,000 to 700,000 years when the Temblor Sea was choppy enough to prevent sediments from settling. As a result, the bones collected on the seafloor where they were churned about and formed a large underwater pile of remains.

Find out more: Fossil bone bed helps reconstruct life along California's ancient coastline

Photo © Nick Pyenson / University of British Columbia.