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Archive for November, 2005

Fall 2005

28 Nov

The Mammoth News

Fall 2005, Volume 10

Lab Work

We now have an extended lab – it’s the Science Center garage where our skull block resides. The focus this term was to unwrap and begin to remove matrix from this block of loess that we knew contained two tusks, two teeth from the upper jaw, the right femur, and presumably the skull. From the curve of the tusks and the position of the teeth, we know that this skeletal block is upside down. The tusks, teeth, and skull are still connected as they were in life (articulated) so we want to keep them together as we proceed.

We have temporarily discontinued work at the excavation site while we work on the skull block. There are currently no bones exposed at the site, however, we are fairly certain that more bones are out there. This was indicated by a ground penetrating radar survey performed in Spring 2004. We have found 120 bones or bone fragments to date, but that’s only half of the mammoth’s bones.

In the first few days of the term, the class unwrapped the skull block, removing the straps, wood frames, Styrofoam, and the upper part of the plaster jacket. Then they started scraping away the matrix (loess) using trowels. We wet the matrix with water or denatured alcohol to reduce the vibration as we scraped. As new bone or tusk was exposed each day, it was impregnated with a consolidant, Butvar, to harden the bone both on the inside and the surface.

Tusks

As we exposed the tusks, the exterior held together fairly well except in a few areas. We exposed the right tusk down to its tip and found that it tapers, which indicates that it was not broken. While some mammoths at age 41 might have longer tusks (up to 8 feet), it is not uncommon to find them shorter. This is because they used their tusks, thus causing them to wear down.

Skull

As we exposed the skull, we were pleased with its condition. The skull bone is fairly solid, although the honeycomb structure of the interior, which is quite fragile, is exposed in places. The skull appears to be somewhat compressed and at an angle to vertical. The entire skull block lists to the mammoth’s left a bit. We have yet to get down to the paleosol, at which point we will see how compacted the skull is.

Other Bones

We have exposed the right femur (upper leg bone) that lies lengthwise between the two tusks with one end (proximal) lying under the right tusk. It is in good condition. We discovered and exposed most of the right tibia adjacent to the femur and between the tusks; one end (proximal) extends under the left tusk. In addition we found two rib fragments, another rib that was an extension of one previously removed from the pit, and two unidentified ends of bones that have not been fully exposed.

Radiocarbon Dating

We have been attempting to get radiocarbon dates on the teeth and on the soil material (paleosol) on which the bones lie. We just learned that we must resample the soil material because there was insufficient carbon in the first sample. This will have to wait until spring.

A tooth fragment from the lower jaw was submitted for radiocarbon dating to the Center for Accelerator Mass Spectrometry at Lawrence Livermore National Lab in California. Kena Fox-Dobbs, graduate student of Paul Koch, Geology Professor at University of California at Santa Cruz, prepared the samples. We are grateful to a Principia parent who underwrote some of the expenses for this work and to these labs that contributed time and supplies to the project as well.

An initial sample of tooth dentine was analyzed and yielded a date of 17,810 +/- 4300 radiocarbon years before present. This corresponds well to our estimate of 17,500 years that was based on stratigraphic control (the mammoth’s position in the Peoria Silt it is buried in), but it has a large margin of error. A second sample of tooth enamel was analyzed and yielded a date of 15,380 +/- 60 radiocarbon years before present. It is known that enamel is more susceptible to alteration by weathering than the dentine, which is on the interior of the tooth, and therefore an enamel date is less reliable and likely to be younger than reality.

At this point, the best we can say is that our mammoth is about 17,500 radiocarbon years old, based primarily on the stratigraphic context and supported, weakly, by the dentine date.

Outreach

Visitors

We had about 125 visitors during the term, including Girl Scouts, Upper School Physics students, Fox River Country Day School students, the American Association of University Women-Jerseyville Chapter, and many local visitors.

Talks

Janis Treworgy gave a presentation on our mammoth project at the Second International Congress of “World of Elephants” held in Hot Springs, South Dakota, home of The Mammoth Site where 55 mammoths have been found in an ancient sinkhole. Many of the same mammoth experts who were at the mammoth conference in the Yukon in 2003 were present at this conference. There was a wealth of information shared both formally and informally. A number of attendees commented on the high quality of our project. A state university in Washington is modeling a dig site they are running after our project, using our web page as a prime resource.

Janis gave a talk on the project to the Principia Club in Houston in October. Janis also gave a talk to the Jerseyville Chapter of the American Association of University Women.

Jeff Saunders and Janis were honored guests at the Quarterly Meeting of the Calhoun County Historical Society for their work in helping to find information about and locate the excavated bones of a mammoth that was only partially excavated in 1940 near Belleview, Calhoun County.

-Janis Treworgy

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