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Archive for November, 2006

Fall 2006

28 Nov

The Mammoth News

Fall 2006, Volume 13

Lab Work

This term we made great progress in the lab and on the skull block, which is still in the Science Center garage. In the lab students finished preparing (cleaning and consolidating) both kneecaps (patellae) and the left upper arm bone (humerus), all tedious tasks requiring lots of patience and careful work. Then we built the storage jacket for the humerus, complete with support legs.

We also finished removing the jacket from the right shoulder blade (scapula), and a couple of students spent their term removing matrix (dirt) from the bone and consolidating it. This turned out to be a harder job than expected because the bone was so deteriorated that there were holes in the bone an inch in diameter in several places. The bone is now clean and well consolidated.

We turned over the left femur at the beginning of the term and removed the rest of its field jacket. Students worked on preparing this side. A bit more work remains to be done.

In the garage, another crew worked on the skull block. Our goal was to finish reducing the size of the block so that we could consider flipping it over perhaps in the spring. The rest of the matrix around the skull was removed and the bone consolidated. Several ribs that continue under the skull block and that had been partially jacketed were removed (the bones had to be cut) and their plaster jackets completed.

The big task was to remove the right upper leg bone (femur) from the block. First we had to separate the femur from the right tusk; it was a happy day when we could see light between them and not have the tusk fall apart. We also had to separate the other end of the femur from the lower leg bone (tibia) that lies partially under the left tusk. Once this was complete, the femur ends were plaster jacketed and the femur removed to the lab. Our plan was to remove the tibia as well, but as we dug around the other end of the tibia, we discovered another bone – perhaps the other lower leg bone (fibula)? – beneath and in contact with the tibia. So we are leaving the tibia in the skull block and will work on removing it after the block has been turned over.

Two students worked on the design of the cribbing to be built up around the block in preparation for turning the block over. Materials were purchased and initial preparations begun.

Optical Stimulated Luminescence Date

Last spring two samples of the loess matrix entombing the mammoth were collected by Dr. David Grimley of the Illinois State Geological Survey. Samples were ten feet apart and directly above the ancient soil (paleosol) on which the bones have been found. This loess should have been deposited shortly after the mammoth’s demise so as to preserve the bones as well as they have been preserved.
These loess samples were dated by Dr. Paul Hanson in the School of Natural Resources at the University of Nebraska in Lincoln using optically stimulated luminescence. The luminescence age tells us when the samples were last exposed to daylight. For this reason, the samples were not exposed to light until light was applied in the lab, at which point energy accumulated in crystal lattices of minerals during burial was released and an age determined.
The dates on our two samples were 1600 years apart, which is within the standard error for this method, and averaged at 17,300 +/-1800 radiocarbon years. This date corresponds well with our date of 17,500 radiocarbon years using the mammoth’s stratigraphic position within the Peoria loess and is close to the radiocarbon age determination on poorly preserved collagen from the tooth dentine of 17,810 +/- 4300 radiocarbon years. So we are now more confident in stating that our mammoth lived about 17,500 radiocarbon years ago.

Outreach

Visitors

During this term we hosted two Cub Scout troops, the Principia 4th graders, and 4th graders from Wilson School also in the St. Louis area; students in the mammoth class gave these tours of both the lab and the skull block in the garage. Janis gave additional tours to parents of new students in the pre-fall and to attendees of the Hill Prairie Conference, hosted by the Biology and Natural Resources Department on campus. Visitors totaled 250 for the term.

Talk

Janis gave a talk at Washington University in St. Louis to the Eastern Missouri Society of Paleontology.

Scientific Paper

Janis has published a paper about our mammoth in a peer-reviewed journal, Quaternary International, published by Elsevier. Quaternary is the time period covering the last two million years, from the ice age to the present. Here is the reference:

Mammoth (Mammuthus sp.) excavation on a college campus in Western Illinois, USA, by Janis D. Treworgy, Jeffrey J. Saunders, and David A. Grimley, Quaternary International (2006), doi:10.1016/j.quaint.2006.08.001

-Janis Treworgy

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