A Visit to Sharktooth Hill

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Visions of Megalodon: A Visit to Sharktooth Hill

The day's first megalodon
A typical specimen of C. megalodon. Photo (c) 2012 Andrew Alden, licensed to About.com (fair use policy)

Sharktooth Hill is a famous fossil locality in the Sierra Nevada foothills outside Bakersfield, California. Collectors find fossils of a large number of marine species here from whales to birds, but the iconic fossil is Carcharodon/Carcharocles megalodon. The day I joined a fossil-hunting party, the cry of "meg!" went up whenever a C. megalodon tooth was found. This was the day's first meg, a small side tooth from the great shark's jaw.

02
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Sharktooth Hill Geologic Map

Rocks and geography of Sharktooth Hill
Derived from the state of California's interactive geologic map

Sharktooth Hill is an area of land south of Round Mountain underlain by the Round Mountain Silt, a unit of poorly consolidated sediment between 16 and 15 million years old (the Langhian Age of the Miocene Epoch). On this side of the Central Valley the rocks dip gently to the west, so that older rocks (unite Tc) are exposed on the east and younger ones (unit QPc) are on the west. The Kern River cuts a canyon through these soft rocks on its way out of the Sierra Nevada, whose granitic rocks are shown in pink.

03
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Kern River Canyon Near Sharktooth Hill

How the bonebeds are being uncovered
Kern River and terrace of late Cenozoic sediments. Photo (c) 2012 Andrew Alden, licensed to About.com (fair use policy)
As the southern Sierras continue to rise, the vigorous Kern River, with its narrow strip of forest, is cutting a wide floodplain between high terraces of Quaternary to Miocene sediments. Subsequently erosion has been cutting into the terraces on either bank. Sharktooth Hill is on the northern (right) bank of the river.
04
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Sharktooth Hill: The Setting

Central Valley rangeland
Click the photo for the full-size version. Photo (c) 2012 Andrew Alden, licensed to About.com (fair use policy)
In late winter the Sharktooth Hill area is brown, but wildflowers are on their way. At right in the distance is the Kern River. The Southern Sierra Nevada rises beyond. This is dry ranchland owned by the Ernst family. The late Bob Ernst was a noted fossil collector.
05
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Buena Vista Museum

Buena Vista Museum
The Museum is dedicated to a wide range of interlocking sciences. Photo (c) 2012 Andrew Alden, licensed to About.com (fair use policy)

Fossil collecting trips to the Ernst family property are administered by the Buena Vista Museum of Natural History. My fee for the day's dig included a year's membership in this excellent museum in downtown Bakersfield. Its exhibits include many startling fossils from Sharktooth Hill and other Central Valley localities as well as rocks, minerals and mounted animals. Two volunteers from the Museum monitored our digging and were free with good advice.

06
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Slow Curve Quarry on Sharktooth Hill

Slow Curve quarry at Sharktooth Hill
Slow Curve has the easiest access, a concern on days when rain threatens to turn the road into slippery clay. Photo (c) 2012 Andrew Alden, licensed to About.com (fair use policy)
The "Slow Curve" site was our destination for the day. A low hill here was excavated with a bulldozer to remove the overburden and expose the bonebed, a widespread layer less than a meter thick. Most of our party chose digging spots along the base of the hill and along the outer rim of the excavation, but the "patio" in between is not barren ground, as the next picture will show. Others prowled outside the quarry and found fossils, too.
07
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Fossils Exposed by Rainwash

Free at last
I found this at the end of the day, making a last pass through the "patio.". Photo (c) 2012 Andrew Alden, licensed to About.com (fair use policy)
Rob Ernst enticed me to start my day in the "patio" by leaning over and picking up a shark tooth right off the ground. Rainfall washes many small specimens clean, where their orange color stands out against the gray silt around them. Teeth range in color from white to black through yellow, red and brown.
08
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First Shark Tooth of the Day

The sharks are still biting
A sharktooth protrudes from its clean silt matrix. Photo (c) 2012 Andrew Alden, licensed to About.com (fair use policy)
The Round Mountain Silt is a geologic unit, but it's hardly rock. The fossils sit in a matrix not much stronger than beach sand, and shark teeth are easy to extract undamaged. You just have to notice the sharp tips. We were advised to be careful with our hands when sifting this material—"the sharks still bite."
09
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My First Shark Tooth

Clean as a hound's tooth
Photo (c) 2012 Andrew Alden, licensed to About.com (fair use policy)

It was the work of a moment to free this pristine fossil from its matrix. The fine grains visible on my fingers are classified by their size as silt.

10
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Concretions on Sharktooth Hill

Some concretions enclose bones, other nothing
Most Sharktooth Hill fossils are too fragile and fragmentary to collect. Photo (c) 2012 Andrew Alden, licensed to About.com (fair use policy)

Slightly above the bonebed, the Round Mountain Silt has concretions, sometimes quite large. Most have nothing in particular inside them, but some have been found to enclose large fossils. This meter-long concretion, just lying around, exposed several large bones. The next photo shows a detail.

11
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Vertebrae in a Concretion

Marine mammals abounded here
These probably belong to a small whale. Photo (c) 2012 Andrew Alden, licensed to About.com (fair use policy)
These vertebrae appear to be in articulated position, that is, they lie exactly where they lay when their owner died. Besides shark teeth, most of the fossils at Sharktooth Hill are bone fragments from whales and other marine mammals. Nearly 150 different species of vertebrates alone have been found here.
12
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Hunting the Bonebed

Join the crowd
Hunting my own bit of bonebed. Photo (c) 2012 Andrew Alden, licensed to About.com (fair use policy)
After an hour or so of sifting through the "patio" sediment, I relocated to the outer rim where other diggers were also having success. I cleared a patch of ground a decent distance away and set in to dig. Conditions at Sharktooth Hill can be ferociously hot, but this was a pleasant, mostly overcast day in March. Although much of this part of California contains the soil fungus that causes valley fever (cocciodiomycosis), the Ernst Quarry's soil has been tested and found clean.
13
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Sharktooth Hill Digging Tools

Digging tools
An array of power tools—human powered. Photo (c) 2012 Andrew Alden, licensed to About.com (fair use policy)

The bonebed is not especially hard, but picks, large chisels and crack hammers are useful as well as shovels in breaking up the material into large chunks. These can be then gently pulled apart without harming fossils. Note the knee pads, for comfort, and the screens, for sifting out small fossils. Not shown: screwdrivers, brushes, dental picks and other small tools.

14
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The Bonebed

The bonebed emerges
First exposure of the Sharktooth Hill bonebed. Photo (c) 2012 Andrew Alden, licensed to About.com (fair use policy)
My pit soon uncovered the bonebed, an abundance of large orange bone fragments. In Miocene times, this area was so far offshore that bones were not quickly buried by sediment. Megalodon and other sharks fed on sea mammals, as they do today, breaking many bones and scattering them. According to a 2009 paper in Geology (doi: 10.1130/G25509A.1), the bonebed here has about 200 bone specimens per square meter, on average, and may extend well over 50 square kilometers. The authors argue that almost no sediment came here for more than half a million years while the bones piled up.

At this point I started to work mostly with a screwdriver and brush.

15
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Scapula Fossil

A shoulder bone unveiled
I cleaned the surface of this bone with a screwdriver and brush. Photo (c) 2012 Andrew Alden, licensed to About.com (fair use policy)
Gently I uncovered a set of random bones. The straight ones are probably ribs or jaw fragments from various marine mammals. The odd-shaped bone was judged by me and the leaders to be a scapula (shoulder blade) of some species. I resolved to try to remove it intact, but these fossils are quite fragile. Even the abundant shark teeth often have crumbly bases. Many collectors dip their teeth in a glue solution to hold them together.
16
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Field Preservation of a Fossil

Holding a delicate bone together
The coat of glue is no guarantee against breakage, but breakage is guaranteed without it. Photo (c) 2012 Andrew Alden, licensed to About.com (fair use policy)
The first step in handling a fragile fossil is to brush it with a thin coat of glue. Once the fossil is removed and (hopefully) stabilized, the glue can be dissolved and a more thorough cleaning performed. Professionals encase valuable fossils in a thick jacket of plaster, supplies that I did not have, nor did I have the time to do things so well. Some day I will see what shape it's in after the long drive home—clearly fossil collecting is more than just digging and picking things up.
17
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End of the Day

Time to go, guy
Some "regulars" can't tear themselves away from Sharktooth Hill. Photo (c) 2012 Andrew Alden, licensed to About.com (fair use policy)
By the end of the day, we had left an impression on our edge of Slow Curve Quarry. It was time to leave, but not all of us were totally worn out yet. Among us, we had hundreds of shark teeth, some seal teeth, dolphin earbones, my scapula, and lots more indeterminate bones. For my part, I was grateful to the Ernst family and the Buena Vista Museum for the privilege of paying to practice on a few square meters of this huge, world-class fossil site.
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Alden, Andrew. "A Visit to Sharktooth Hill." ThoughtCo, Feb. 28, 2017, thoughtco.com/visit-to-sharktooth-hill-1440566. Alden, Andrew. (2017, February 28). A Visit to Sharktooth Hill. Retrieved from https://www.thoughtco.com/visit-to-sharktooth-hill-1440566 Alden, Andrew. "A Visit to Sharktooth Hill." ThoughtCo. https://www.thoughtco.com/visit-to-sharktooth-hill-1440566 (accessed November 22, 2017).