Field Trip To The Kettleman Hills Fossil District, California

A Pliocene classic: 4.5 to 2.5 million year-old fossils

Contents For Kettleman Hills Fossils Field Trip:

Introduction Text: The Field Trip   Images: On-Site Images: Fossils

  Images: Bonus Material   Kettleman City Weather Links: My Music    Enail Address

Introduction

Please Note: Unauthorized fossil collecting in the Kettleman Hills is mostly verboten, prohibited. For localities that lie on private property and land held by a well-known oil company, visitors must first secure in writing formal permission from the land owners. Of the fossil localities discussed here, only one at last field check required prior permission from the oil corporation. Always conduct due diligence before collecting in any given area.

Health Advisory: And now for the obligatory words of caution. Endemic to the Kettleman Hills and the southern San Joaquin Valley of California, in general, is Valley Fever. This is a potentially serious illness called, scientifically, Coccidioidomycosis, or "coccy" for short; it's caused by the inhalation of an infectious airborne fungus whose spores lie dormant in the uncultivated, harsh alkaline soils. When an unsuspecting and susceptible individual breaths the spores into his or her lungs, the fungus springs to life, as it prefers the moist, dark recesses of the human lungs (cats, dogs, rodents and even snakes, among other vertebrates, are also susceptible to "coccy") to multiply and be happy. Most cases of active Valley Fever resemble a minor touch of the flu, though the majority of those exposed show absolutely no symptoms of any kind of illness; it is important to note, of course, that in rather rare instances Valley Fever can progress to a severe and serious infection, causing high fever, chills, unending fatigue, rapid weight loss, inflammation of the joints, meningitis, pneumonia and even death. Every fossil prospector who chooses to visit the Kettleman Hills and southern San Joaquin Valley must be fully aware of the risks involved.

An introductory sampling of sand dollars and pectens (scallop shells) from the world-famous Pecten Zone of the Middle Pliocene San Joaquin Formation, North Dome area, Kettleman Hills, California. All the sand dollars can be referred to Dendraster coalingensis. The pectens are called scientifically, Pecten coalingensis.

An introductory sampling of pelecypods from the Upper Mya Zone of the Middle Pliocene San Joaquin Formation, South Dome area, Kettleman Hills California. All the following are called scientifically, Macoma affinis: Top row--middle and far right; middle row--third from the left; bottom row--third and fourth from left. All the remaining clams are Mya dickersoni.

Take The Field Trip

Back in 1940, the United States Geological Survey (USGS) issued Professional Paper 195 by W.P. Woodring, Ralph Stewart and R.W. Richards, entitled: Geology of the Kettleman Hills Oil Field, with the subtitle Stratigraphy, Paleontology, and Structure. That's still pretty much the definitive geological and paleontological statement on the Kettleman Hills region. It's a classic work of science that continues to draw inquisitive paleontology enthusiasts/sleuths to university reference libraries all across America, seeking information on what kinds of fossils can be collected there--and just where such magnificently preserved material can be found.

For that data, you need to thumb all the way to back of the paper, through all of those stunning black and white photographs of Kettleman Hills fossils--all of those perfectly preserved sand dollars and pectens and clams and snails and such that truly boggle the mind and catch one's attention, holding it for lengthy periods of time, delaying the search for the exact localities from which the specimens came. When you finally get to the back of Professional Paper 195, one half expects to learn that most of the fossils likely came from no more than a dozen or so localities, 20 to 30 at most, perhaps (I am speaking from experience--this was my grand delusion, at least)--and so, it comes as a pleasant shock to learn that the Kettleman Hills, an area roughly 20 miles long by 4 miles wide situated some 80 miles northwest of Bakersfield in Kings County, California, contain 370 registered fossil localities in the Pliocene (5.3 to roughly 2.5 million years old) Tulare, San Joaquin and Etchegoin Formations (in descending order of geologic age--that is, from youngest to oldest)--an amazing array of invertebrate, vertebrate and even floral fossil remains that includes pectens (scallop shells), clams, gastropods, oysters, mussels, fish, land mammals, marine mammals, sand dollars, diatoms and even terrestrial plants, among others.

Of course, the majority of those 370 specific fossil localities are no longer accessible to the general public; many remain closed due to legal liability issues incurred by local property owners, while others were obliterated long ago through the vagaries of time. Most Kettleman Hills paleontolgical places of interest, still potentially open for inspection, currently lie on private property. That means, naturally enough, that if you've failed to secure the essential preliminary formal written permission from the proper authorities (the legal property owners), don't even think about wandering off the main asphalt paths to seek out potential fossil-bearing places. One will likely face certain prosecution if one misbehaves here.

The three specific sites described here provide a representative sampling of the kinds of fossils that can be found in the Kettleman Hills area, as each is loaded with abundant, sensationally preserved specimens. At last field check, only one of the localities requires advance written documentation from the local oil corporation.

Probably the best of the lot, in terms of overall specimen variety and quality of fossil preservation, is what many paleontology enthusiasts refer to as--in an affectionate, colloquial sense-- "The Zone." The fish remains, pectens, oysters and sand dollars found there occur in the Middle Pliocene San Joaquin Formation, which is roughly three million years old, and the Upper Pliocene Tulare Formation, around two and a half million years ancient. It lies back in the Kettleman Hills on private property, so permission must be secured from the oil company branch office. Usually, though, that is not a problem. In any event, the bottom line here is: You certainly must possess written approval from the oil corporation folks before visiting "The Zone" locality.

Averaging 10 to 20 feet in thickness, the fossiliferous "Zone" horizon is a sequence of gray to tan silts and sands exposed for a length of a half to three-quarters of a mile--it is, in fact, an amazingly fossiliferous extension of the famous Pecten Zone in the Middle Pliocene San Joaquin Formation. And it is crammed almost everywhere one happens to look with perfectly preserved scallops, oysters and sand dollars, primarily, whose original shell material has been preserved intact.

In addition to the wonderful inverbrate animal assemblage here, one is also advised to stay alert for occasional beaver teeth--vertebrate remains that invariably, while on Public Lands, one must leave alone, never collect except by formal written permission from the Bureau of Land Management; but there, you happen to fossil hunt on private property belonging to the oil folks, and if you've successfully garnered the essential written documentation from their branch office (let's hope that you have; one needs to carry the paper at all times while on oil company land, or risk almost certain detention by the local law enforcement authorities while they decide whether to cite you for "simple" misdemeanor trespass, or perhaps even criminal trespass), you have secured the right to keep whatever fossils you happen to find, including vertebrate remains usually off-limits to unauthorized individuals.

At "The Zone" locality, the sand dollars measure on average from a half-inch to two inches in diameter, although many are quite minute--what you might call "sand pennies," if you will--in the neighborhood of no more than a quarter-inch across. All such echinoid occurrences here are referable to one or two species of the genus Dendraster, mainly Dendraster coalingaensis. The scallop, or pecten shells are striking, attractive specimens whose ribbed exteriors are of course very distinctive and identifiable in the sediments; most of them belong to the species Pecten coalingensis. An added collecting plus here is that the majority of fossils either weather out of the San Joaquin Formation already intact, or can be dug out without any degree of pain or strain. All that's needed to put the finishing, cleaning touches on them is a gentle scrubbing in water with an old toothbrush.

In addition to the pectens, oysters, sand dollars and beaver teeth teeth, another fossil type can be also found in the same general area of "The Zone" locality--fish remains. The specific horizon in which they occur has been mapped as the Upper Pliocene Tulare Formation, which is about 2.5 million years old. Geological and paleo-limnological analyses demonstrate pretty convincingly that the Tulare is a fresh to brackish water deposit that incorporates sedimentary facies which record the final drying up of the last great inland sea to cover the present-day Central Valley of California--a sea that throughout the Tertiary Period of the Cenozoic Era (66 to roughly 2.5 million years ago) had at times stretched from Redding (northern California) all the way south to the vicinity of Bakersfield (southern California).

The Tulare Formation of the Kettleman Hills just happens to yield the largest fauna of fresh water Pliocene mollusks of any rock deposit on the US west coast. Some 33 varieties of pelecypods and gastropods have been described from it, though only a few species come from this particular spot near the The Zone. Several miles south of The Zone locality, though, a second Tulare area of exposure yields abundant and well preserved fresh water mollusks.

But here at "The Zone," fish remains are the thing--unusual paleo-items colloquially called "bulbous fish growths" by field geologists who've mapped the geology, structure and stratigraphy of the Kettleman Hills. These are the fossilized bony tumors which evidently afflicted many of the fish during Tulare times. Most specimens are similar to observed types that attack the skeletons of modern weak-fish, cod (specifically the hakes), angel fishes and even catfish. No other fossil locality, save the Kettleman Hills, is known to yield these kinds of paleontological preservations. They are present in fair numbers in the tan silts and sands, most appearing as rounded "bulbous" masses that reveal obvious bony structure on their worn exteriors. A few, though, show a definite resemblance in both shape and size to Brazil nuts. This "bulbous fish growth" zone is perhaps 30 feet thick at the most and trends generally south to southeast for a distance of approximately three-quarters of a mile. The fossilized bony tumors weather free from the easily eroded sediments and presented no difficulty to collect.

While "bulbous fish" growths dominate the Tulare exposures at "The Zone" site, much better preserved pelecypods and gastropods from the Upper Pliocene Tulare Formation occur several miles south in what local geologists call the Middle Dome district of the Kettleman Hills ("The Zone" area lies in what's referred to as the North Dome, by the way). Here, innumerable freshwater gastropods and pelecypods weather out whole and perfectly preserved. And because they're so exceedingly fragile, special care must be taken to prevent them from incurring damage. Probably a good idea is to place the mollusks in a plastic sandwich bag for safe transport back home for a closer inspection. Also present here, in the more indurated (hardened) layers of sandstone, are relatively common specimens of brackish water mussels, most of which occur in an excellent state of preservation. Almost all of the 33 species of freshwater mollusks identified from the Tulare Formation can be collected from this single locality. An obvious distinctive feature of the assemblage is that in general the fossil clams and snails are decidedly diminutive, many no larger than a quarter-inch in length. For this reason, a good-quality hand lens of ten power or better is useful when studying the external details of your finds.

A third accessible and highly fossiliferous locality in the Kettleman Hills occurs several miles south of the Tulare locality; this one's within the Upper Mya Zone of the Middle Pliocene San Joaquin Formation, a place that yields innumerable three million year old pelecypods, many with both valves preserved intact. It occurs in what's called the South Dome area of the Kettleman Hills. Consisting almost entirely of estuarine clams dominated by Mya dickersoni and Macoma affinis, the pelecypodal fossils here are conspicuously abundant, although several intervals reveal only fragmental material. Still, many nice specimens of clams with both valves preserved can be secured by using attentive care and extra patience. Even though it's limited in aerial extent--the fossil-bearing layers outcrop for only a tenth of a mile or so--this isolated exposure of San Joaquin Formation sediments in the Upper Mya Zone provides a maximum of clam-shell density, with Macoma and Mya liberally distributed throughout the brown clays.

Now's probably a pretty good time to warn about a major health risk while collecting fossils in the Kettleman Hills.

It's what's commonly called Valley Fever--a potentially dangerous condition caused by inhalation of an infectious airborne fungus. Not only are the Kettleman Hills affected, but the entire surrounding southern San Joaquin Valley is also infested with the fungal spores which cause Valley Fever, or what the medical community calls Coccidioidomycosis. While most active cases of the illness resemble a slight touch of the flu, or even a minor cold, a small percentage of those infected do indeed go on to develop severe medical complications such as pneumonia, meningitis and even death; a particularly devastating, chronic form of "coccy" mimics the debilitating symptoms of tuberculosis and lung cancer, requiring months of recuperation and rehabilitation. On the other hand, a significant percentage of those exposed to the fierce fungus show absolutely no symptoms of any kind of infection.

In the southern Great Central Valley of California, there is obviously no sure way to avoid exposure to coccy. For one, it resides everywhere in the uncultivated alkaline soils of the southern San Joaquin Valley (it's also endemic to California's Mojave Desert, San Fernando Valley, Santa Clarita Valley, and Coachella Valley--not to mention central to southern Arizona, parts of New Mexico, southern Utah, west Texas, and southern Nevada), and when the winds kick up, throwing dust everywhere, one is almost certain to come in contact with the feared spores. Fortunately, coccy is difficult for most folks to catch (individuals with compromised immune systems seem most vulnerable), and only a minuscule number of those who actually develop active symptoms progress to the most severe complications.

This is all something to consider when stirring up dust at the Kettleman Hills fossil localities, where in deference to coccy's potential virulence many collectors choose to wear surgical masks while excavating specimens.

If contending with Valley Fever fungal spores was not enough, visitors to the Kettleman Hills experience even more obstacles to paleontological nirvana. Although fossil collecting in the Kettleman Hills can be done year-round, a couple of seasons in California's Central Valley are notorious for, one, taxing bodily comfort and, two, interfering with driving safety. Summertimes, for example, are invariably ultrahot--downright savagely hot, as a matter of fact--with daytime temperatures more like extreme desert conditions than any other geographic comparison that comes to mind. And there is no shade to speak of in the hills, except for rare oven-tolerant shrubs maybe two feet high at most. These are fine for shading the head when lying flat on one's back, when prostrate, but rather puny for providing overall precautionary protection from the elements. And while winters are usually mild, with regular seasonal rainy patterns and tolerable temperatures, a particularly impenetrable fog traditionally inhabits the Great Central Valley during December and January--the infamous Tule Fog. It clamps down tight on the entire San Joaquin Valley region for days on end, at times reducing visibilities to zero. Needless to report, driving during the reign of the Tule Fog is hazardous and harrowing. And the Kettleman Hills, lying on the west side of the Central Valley, do not seem to be exempt from these fogged conditions. Proceed at your own risk then.

When collecting in the Kettleman Hills, be sure to obey all the rules and regulations. Obtain written permission from the oil company officials where necessary, and don't enter private property without the owner's say-so. Of the three fossil localities described here, only "The Zone" requires permission from the oil corporation folks.

Happy collecting in the Kettleman Hills. But bring along a hat and plenty of water in the summer. And a searchlight during December--you never know when you might want to try to find the end of your own nose in the Tule Fog.

On-Site Images

Click on the images for larger pictures

Click on the image for a larger picture. A Google Earth street car perspective that I edited and processed through photoshop. This is a view slightly west of north to the North Dome area of the Kettleman Hills, California. Rocks underlying the hills include the Lower Pliocene Etchegoin Formation and the Middle Pliocene San Joaquin Formation--both of which yield locally abundant fantastically well preserved fossils--including sand dollars, scallop shells (pectens), gastropods, and clams.

Click on the image for a larger picture. A seeker of Pliocene paleontology explores the famous Pecten Zone in the Middle Pliocene San Joaquin Formation, at the "The Zone" locality, North Dome area, Kettleman Hills, California. It is very difficult to traverse this slope without stepping on the whole, perfect Dendraster coalingensis sand dollars that have weathered out of the fine silts and sands some three million years old. Abundant perfectly preserved scallop shells (pectens) also occur here, all weathering free from the fine silts and sands of the San Joaquin Formation. About a quarter mile east of here, exposures of the Lower Pliocene Etchegoin Formation produce beaucoup Dendraster gibbsii sand dollars--one of the most highly prized echinoids in the world. And just west of this fossil site the Upper Pliocene Tulare Formation contains the curious "bulbous fish growths"--bony tumors that afflicted several species of esturarine fish some two and a half million years ago.

Click on the image for a larger picture. A Google Street care perspective that I edited and processed through photoshop. The view is due north to a roadcut exposure of the Upper Pliocene Tulare Formation in the Middle Dome, Kettleman Hills, California. Here the Tulare yields over 30 species of fresh water gastropods and pelecypods--more kinds of fresh water mollusks, as a matter of fact, than any other Pliocene-age rock formation on the US west coast.

Click on the image for a larger picture. A Google Earth street car perspective that I edited and processed through photoshop. The view is slightly west of north to exposures of the Middle Pliocene San Joaquin Formation, Middle Dome area, Kettleman Hills, California. San Joaquin strata in middle ground belong to the Neverita Zone, which here produces abundant beautifully preserved gastropods of the Neverita reclusiana variety.

Click on the image for a larger picture. A Google Street car perspective that I edited and processed through photoshop. The view is practically due south through a roadcut in the Upper Mya Zone of the Middle Pliocene San Joaquin Formation, South Dome area, Kettleman Hills, California. Profusely productive pockets of pelecypodal perfection occur here, yielding numerous specimens of the clams Mya dickersoni and Macoma affinis with both valves preserved intact.

Click on the image for a larger picture. A Google Earth street car perspective that I edited and processed through photoshop. A quintessential scene in California's Great Central Valley, captured by a Google Earth car along California State Route 41 just south of Kettleman City. The view is slightly east of due north to a commercial fruit orchard that spreads through the fertile flatlands.

Images Of Fossils From The Kettleman Hills

Click on the images for larger pictures

Click on the image for a larger picture. A pectin (scallop) shell from the Pectin Zone of the Middle Pliocene San Joaquin Formation--"The Zone" fossil locality, North Dome area, Cattleman Hills, California. Called scientifically Pectin coalingensis. 

Click on the image for a larger picture. This is a sand dollar from the Pectin Zone of the Middle Pliocene San Joaquin Formation--"The Zone" fossil locality, North Dome area, Cattleman Hills, California. Called scientifically, Dendraster coalingensis.

  Click on the image for a larger picture. Here's a sand dollar from the Lower Pliocene Etchegoin Formation, near "The Zone" fossil locality, North Dome area, Cattleman Hills, California. Called scientifically, Dendraster gibbsii.

Click on the image for a larger picture. A gastropod from the Neverita Zone of the Middle Pliocene San Joaquin Formation, Middle Dome area, Kettleman Hills, California. Called scientifically, Neverita reclusiana.

Click on the image for a larger picture. Oysters from the Pecten Zone of the Middle Miocene San Joaquin Formation--"The Zone" fossil locality, North Dome area, Kettleman Hills, California. Called scientifically, Ostrea vespertina sequens.

Click on the image for a larger picture. A pelecypod with both valves preserved intact from the Upper Mya Zone of the Middle Miocene San Joaquin Formation, South Dome area, Kettleman Hills, California. Called scientifically, Macoma affinis.

Click on the image for a larger picture. A "bulbous fish growth" from the Upper Pliocene Tulare Formation, near "The Zone" fossil locality, North Dome area, Kettleman Hills, California. This is a fossilized bony tumor that afflicted a fish that lived some three to two and a half million years ago in the estuaries bordering a great inland sea in what is now the Central Valley of California. Most of the fossil tumors are similar to observed types that attack the skeletons of modern weak-fish, cod (specifically the hakes), angel fishes and even catfish. No other fossil locality, save the Kettleman Hills, is known to yield these kinds of specimens. 

Click on the image for a larger picture. Fossil fresh water gastropods from the Upper Pliocene Tulare Formation, Middle Dome area, Kettleman Hills, California. Called scientifically, Physa wattsi.

Fossils From The Vicinity Of The Kettleman Hills, California

Bonus paleontological material

Water Beetle 

 Sand Dollars

 Giant Oyster

Turritellas; Barnacles

 Turritella Snails

Kettleman City Weather

Find more about Weather in Kettleman City, CA
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Weather for the community of Kettleman City, which lies along the eastern side of the Kettleman Hills. Along with Avenal to the west, Kettleman City is a gateway for the Kettleman Hills paleontological paradise.

My Music Pages

In addition to my many Web pages pertaining to matters paleontological and geological, I also have 9 sites up and running that feature my solo, acoustic, instrumental 6 and 12-string guitar playing--in addition to songs I have recorded with my parents over the years (family music) And it's all free music--for listening and for downloads of the mp3 files.

Jump on over to The Acoustic Guitar Solitaire Of Inyo--A Cyber-CD for 30 covers of some of my favorite songs--all played on a 1976 Martin D-35 6-string guitar.

For 32 mp3 selections of original compositions and covers of some of my favorite songs--all played on a 1970 Stella 12-string guitar, a 1976 Martin D-35 guitar and a Sigma DMISTCE guitar, head on over to Beyond The Timberline--A Cyber-CD .

At The Distant Path--A Cyber CD listen to me play 32 covers and original compositions on a 1976 Martin D-35, a Sigma DMISTCE 6-string guitar and a 1970 Stella 12-string guitar.

Over at Inyo And Folks--A Musical History I've created a page that features 110 songs I recorded with my parents--all played on acoustic 6 and 12-string guitars, banjo, kazoo, maracas. and tambourine.

Go to Acoustic Stratigraphy: I play 34 covers of some of my favorite songs on acoustic 6 and 12-string guitars.

Back To Badwater--A Cyber-CD: Listen to me play 32 covers and original compositions on 6 and 12-string guitars; it's all free music.

For an all-text page that includes all 332 of my guitar mp3 files placed on the Internet, go to All Inyo All The Time. That's where you'll find access to all of my musical selections, in order of their appearance on the Web--from my first Cyber-CD ("The Acoustic Guitar Solitaire Of Inyo") to the last, "The Rarities And Alternate Recordings Of Inyo."

Inyo 7--A Cyber CD: Listen to me play 30 covers of some of my favorite songs, plus originals.

The Rarities And Alternate Recordings Of Inyo--A Cyber-CD Listen to me play 32 seldom-heard, rare, alternate recordings of some of my previously released tracks.

Jump on over to my page It's A Happening Thing--Music From The Year 1967. Includes YouTube (and other sources) links to all songs that charted US Billboard Top 100 in year 1967 (close to a thousand, as as matter of fact), plus links to records that bubbled under US Billboard's Hot 100 charts that year (releases that placed #101 to #135); peruse, too, my extensive personal database of year 1967 music.

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