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Fossils from Beecher's Trilobite Bed can be "pyritized", spectacularly preserved with fool's gold. Photo of Yale Peabody Museum specimen YPM 228 courtesy Dr. Susan Butts.

Yale Peabody Museum of Natural History

Beecher's Trilobite Bed

Buried underground, near Utica, New York, lies a 455 million year old treasure. At the bottom of a deep ocean where oxygen was very scarce, lived trilobites and a few other types of animals who were fossilized in pyrite, a.k.a. "fool's gold." During the Late Ordovician, upstate New York was covered by an ocean trench which formed when continental plates to the east were colliding with North America. The collision uplifted the Appalachian Mountains and a bowed the ground to the west to create a trough-shaped ocean named the Taconic Foreland Basin. Sediment shedding off those growing mountains was washed into the basin, often as turbidites—mud-laden currents flowing from shallow to deep water.


The Beecher's Trilobite Bed fossil site was found by William Valiant of Rutgers College in September 1892 and was soon visited by Charles E. Beecher, the Curator of Geology at the Yale Peabody Museum from 1891-1904. Beecher studied and collected extensively, under the direction of O.C. Marsh. Beecher was the first to report the existence and details of trilobite appendages and features from the animal's underside, like gills. Over the course of decades, the precise locality of the original quarry was lost to scientists. Through clever and diligent work, amateur collectors Thomas Whiteley and Daniel Cooper were able to track down the original site, which was long since overgrown. In 1989, the site underwent a major excavation under the direction of the Smithsonian Institution (Washington, D.C.) and the American Museum of Natural History (New York City). More recently, Yale Peabody Museum Director and Invertebrate Paleontology Curator Derek E.G. Briggs, along with his graduate students, have worked on the process of pyrite replacement and the paleoecology of the Beecher's Trilobite Bed.

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Charles Emerson Beecher visited the famous fossil beds that now bear his name between 1891 and 1904 (left).
The site was rediscovered and excavated in 1989 (right). Photos courtesy of the Yale Peabody Museum.

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Fossils from Beecher's Trilobite Beds are famous for their exceptional preservation by pyritization. Even "soft parts", like these gills, were preserved—an unusual occurence. Photo of Yale Peabody Museum specimen YPM 228 courtesy Dr. Susan Butts.

Pyritization: Preservation with Fool's Gold

The environment in which these trilobites lived was rich in iron and bacteria that broke down organic matter to create sulfide. External trilobite skeletons are made of minerals embedded in chitin, with softer, more flexible legs, antennae and fine features. Usually, the processes of decomposition by microbes, scavenging by other animals, and tossing around in currents tend to destroy animal soft parts (muscles, guts, skin, etc.) and break off appendages in a matter of a few days or weeks, leaving only the hard parts (exoskeletons, shells, interior skeletons including bones and teeth) to fossilize. But in this case, very soon after the death of the animal, the external skeleton and soft parts were replaced with pyrite—an iron sulfide mineral that formed in concert with the bacteria—before the soft tissues decayed. Trilobite fossils were well known before the discovery of those in Beecher's Bed, but the legs and antennae were not preserved, so this was quite an amazing discovery. The fossilization with fool's gold also allows for detailed x-ray photography, like the Triarthrus eatoni (Yale Peabody Museum specimen number 228) pictured below.

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The fossilization with fool's gold also allows for detailed x-ray photography, like this Triarthrus eatoni. X-ray of Yale Peabody Museum specimen YPM 228 courtesy Dr. Susan Butts.


A few other types of fossils are found alongside the trilobites—graptolites, cephalopods, brachiopods, bivalves, algae, and brittle stars. Most specimens are poorly preserved as molds (shells have dissolved, leaving just an impression). Other animals may be partially pyritized, but do not have preservation of the soft tissues. Some beds have fragments of crinoids, trilobites, and other shell material. There are even discoveries of weird unidentifiable arthropods (the group that includes trilobites, bugs, etc.) like a possible crustacean (relative of crab, lobster, and shrimp) bearing over 30 legs!

Fossil Collecting

Collecting fossils is fun and there are lots of places where kids and adults can collect fossils for their own personal collections—but Beecher's Trilobite Bed is not one of them. Fossil collecting on private land and also on National Park Service land is illegal without the owner's permission, or in the case of the National Park Service, a permit. The Beecher's Bed Trilobite quarry is long-since covered and is on private land. Please respect the privacy of private land owners and see these fossils at the Yale Peabody Museum in New Haven, CT and many fantastic photographs of specimens at fossil preparator Markus Martin's website.

Article and photographs provided by Dr. Susan Butts (Yale Peabody Museum of Natural History, Senior Collections Manager). Photographs by T.E. Whiteley, J.L. Cisne, and S. Butts.

2013 Paleozoic Partner feature articles:

| January: Fossils of the 2013 National Fossil Day Artwork | February: Paleontological Research Institution, Museum of the Earth | March: Falls of the Ohio State Park | April: Field Museum of Natural History, Mazon Creek Collection | May: Prehistoric Trackways National Monument | June: Cincinnati Museum Center | July: Glacier Bay National Park & Preserve | August: University of Michican Museum of Paleontology, Silica Formation Fossils | September: Yale Peabody Museum of Natural History, Beecher's Trilobite Bed | October: Guadalupe Mountains National Park | November: Utah Geological Survey, Millard County Cambrian Fossils | December: Denver Museum of Nature and Science, High-Altitude Mass Extinction |

Last updated: September 1, 2013