During the Miocene epoch, the Pacific shoreline lay at the eastern margin of the southern San Joaquin Valley. To the east, where desert landscapes exist today, there was a semi-tropical savanna environment inhabited by camels, horses, tapirs, sloths and elephants. The shallow sea was home to nearly two dozen of species of dolphins, whales, pinnipeds (seals, sea lions and walruses) and other sea-going mammals, including a hippo-like creature called Desmostylus. The fauna also included turtles, crocodiles, and numerous birds. Something needed to fill the slot at the top of the food chain, and given the name of the locality, it isn't too surprisingly a group of sharks. Lots of them; about 27 species of sharks and rays have been discovered here, including the Discovery Channel's favorite, the massive Carcharodon megalodon.
The layers exposed at Sharktooth Hill (along the Kern River upstream of the town of Bakersfield) have yielded up not just thousands of specimens, but hundreds of thousands. In some places, a shovelful of dirt would have hundreds of teeth inside. Numerous studies have been undertaken at the site; a good review can be found here. The national significance of the site was recognized in 1976 as Sharktooth Hill was added to the United States Landmark Registry.
Sharktooth Hill is one of the most important fossil localities in the western United States, and one of the more important fossil collections to have come out of the hill is now being sold by the widow of an amateur paleontologist. The fossils in question have been on public display for a number of years at the CALM Zoo and more recently at the Buena Vista Museum of Natural History. They have hopes of getting the Allodesmus fossil (a primitive sea lion), but the price is too steep for their budget at around $150,000. I hope that some sort of arrangement can be made that will allow the fossil collection to remain accessible to the public. It is a great resource.
The Other California is my continuing series of what to see in our great state when you've visited all the really famous places that show up on all the postcards.
Ah, Garry, you take me back to before I was 8 years old. My mother, a zoology student at "Fresno State" took me to Sharktooth hill, and we spend a day digging for them. We found them. I remember the rocker screen she made to sift through the dirt, and I would watch and wait for it to stop, and pick up the triangular fossils with glee. She set one in some sort of resin in an ice cube tray for me, and I took it to school for show and tell.
ReplyDeleteI really should visit that area some time soon.
All the best,
Edie
Garry,
ReplyDeleteGreat post - glad to see STH getting its due! A couple of things:
1. The Round Mountain Silt is now considered its own formation-level unit that is laterally equivalent to the deeper-water Temblor Formation. This recent USGS Professional Paper has alot of great stratigraphic and other geologic data on the Cenozoic of the San Joaquin Basin (see in particular the papers by Scheirer & Magoon and Johnson & Graham): Petroleum Systems and Geologic Assessment of Oil and Gas in the San Joaquin Basin Province, California
2. For anyone interested more in the fossil deposit itself, there was a paper in Geology last year on how the deposit formed:
Pyenson, N.D., R.B. Irmis, J.H. Lipps, L.G. Barnes, E.D. Mitchell, Jr., and S.A. McLeod. 2009. Origin of a widespread marine bonebed deposited during the middle Miocene Climatic Optimum. Geology 37:519-522. DOI: 10.1130/G25509A.1
Thanks for the stratigraphy update; my source of info was the California Geology article from 1985 or so by Dan Dupra.
ReplyDeleteInteresting, indeed. For a virtual field trip to the Sharktooth Hill Bone Bed, visit my page over at http://inyo.coffeecup.com/site/sb/sharkbonebed.html ; includes detailed text, with on-site images and photographs of representative fossils.
ReplyDeleteBy the way, I too still call the bone-bearing unit the Round Mountain Silt Member of the Temblor Formation; it's such a long-held, universally recognized geologic designation. Upgrading the member to formation level was completely unnecessary in my opinion.
The "town" of Bakersfield is more populated then they city of Pittsburg
ReplyDelete