Thursday, December 30, 2010

The Other California: Sharktooth Hill and a Fossil Collection in Need of a Good Home

Besides the familiar La Brea Tar Pits (translation: "The Tar" Tar Pits), California is not widely known as a treasure trove of fossil discoveries. A little of bit of digging (pun intending) reveals the state as a rich resource of the history of life through time. Death Valley and other parts of the Basin and Range province have been a source of Proterozoic and Paleozoic fossils which are more varied and complete than the assemblage found at Grand Canyon. A few dinosaur bones have been found here and there, but the record of seagoing reptiles is (to me, anyway) even more intriguing: mosasaurs, plesiosaurs and ichthyosaurs. But if you ask paleontologists about the time period with the richest fossil record in California, they may very well mention the Miocene epoch of the Neogene period (5.3 to 23 million years before present). California has some of the thickest sedimentary sequences of Miocene rocks anywhere, including marine and terrestrial environments. A future post may include a discussion of the Ricardo and Barstow formations in the Mojave Desert, but for reasons to be noted in a moment, I want to talk about the Temblor Formation in the Central Valley and Coast Ranges. The Temblor is a sequence of sandstone and siltstone that was deposited in shallow basins offshore in Miocene time, around 15-16 million years ago. A member of the formation, the Round Mountain Silt, is one of the most productive fossil layers in the state.
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.


Edie Howe said...

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.

I really should visit that area some time soon.

All the best,

220mya said...


Great 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

Garry said...

Thanks for the stratigraphy update; my source of info was the California Geology article from 1985 or so by Dan Dupra.

Inyo said...

Interesting, indeed. For a virtual field trip to the Sharktooth Hill Bone Bed, visit my page over at ; includes detailed text, with on-site images and photographs of representative fossils.

By 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.

Anonymous said...

The "town" of Bakersfield is more populated then they city of Pittsburg