Triarthrus eatoni and the OTB
Figure 1. Section of Beecher’s OTB (Original Trilobite Bed) excavated along natural joints in the rock.
Discovered in 1892 by William S. Valiant and made famous by the work of Charles Emerson Beecher, the BTB (Beecher's Trilobite Bed) is located in a small quarry outside of Rome, New York. The layer in which the stunning pyritized trilobites are found is known as the OTB (Original Trilobite Bed), and is represented by a 4cm thick layer of shale that has yielded some of the most spectacular fossils ever found. The most prominent fossil from the OTB is Triarthrus eatoni, an Upper Ordovician trilobite from the Frankfort Shale of the Lorraine Group.
The OTB is a Konservat-Lagerstätte with exceptional soft tissue preservation of antennae, appendages and occasionally egg broods preserved near the underside of the cephalon. There exist only a few sites around the world that preserve this level of detail.
The details of the quarry location were lost when Charles E. Beecher died unexpectedly in 1904. It would take another 80 years for the site to be re-discovered by 2 amateur collectors, Thomas E. Whitely and Dan Cooper. The Yale Peabody Museum became involved with the site and administered it for research projects over the next 20 years.
For the last 15+ years the quarry has been managed by Markus Martin, founder of Gold Bugs. Not only is Markus the owner of Gold Bugs, he is the recognized expert on the preparation of fossils from this site.
To understand how easy it was for the quarry to become lost from record I’ve taken a photo of part of the quarry and of a block from the OTB.
Triarthrus eatoni
Order: Ptychopariida - Family: Olenidae
Age: Upper Ordovician
Locality: Beecher's Trilobite Bed
Formation: Frankfort Shale
Figure 2. Eggs are found beneath the head in the free cheek area and appear as small oval structures.
At the top of the blog figure 1. shows an excavated section of the quarry taken down to the OTB. It should be noted that a section like this takes a good weekend of backbreaking work to excavate! Figures 3. and 4. represent a block of the OTB I took from this actual section. This is a characteristic piece of the bed that is weathered and provides little indication that it is contains the 4cm layer of shale that is the OTB.
Figure 3. Naturally weathered block of OTB taken from the above excavation
Figure 4. Close up of figure 3.
Figures 5. and 6. show the opposite side of the block displayed in figure 3. This side has been polished to reveal the now very characteristic dark line that is the base of the OTB and the coarsely undulating upper limit 4 cm above. A stark contrast to the photos in figures 3. and 4. Is it any wonder that this famous layer of shale was lost for so long!
Figure 5. Polished side of block in figure 3.
Figure 6. Close up of figure 5.
If we take a look at figure 7. we can see the OTB in a little more detail. The thickness of the OTB is represented by the vertical line indicating a total thickness of 4 cm. What’s interesting about this polished section is that the first centimeter up from the base is slightly lighter than the rest of the OTB (You may have to look a little closer to see it). This is the most productive part of the bed, though the remaining 3 cm of shale also preserve pyritized trilobites.
We are fortunate enough to have a variety of fine examples of soft-tissue trilobites from Beecher’s on Fossil Soup thanks to it’s current caretaker - Markus Martin.
Figure 7. Close up look at the OTB
References:
Some of the material in this blog post was sourced from Wikipedia. Click this link for the Wikipedia page: Beecher’s Trilobite Bed