So, as promised, my cabin. There are three of these, with two interns in each, and each has a bathroom, kitchen, living room, washer/drier.... I am going to have a hard time going back to dorm life in the fall. The other interns are a lot of fun to be around, and are all interested in what we are doing and interesting to talk to. We're all from different places and stages in our pursuit in paleontology, and thus its a great time to exchange stories and information and opinions and such. But then, paleontology just tends to require that you have some amount of bonding with those you work (and generally live) with. Its just part of the job.There is a lot of very interesting research here and a lot to try to absorb. After all, a big part of our job here is going to be not just excavating, but also teaching the public about what we are doing. If someone is willing to drive an hour or more out of the way of, well, anything, they better find someone on the other end of that drive willing (and hopefully able) to answer every little question they have, whether its a small child (or uneducated parent) asking "where are the dinosaurs?" or a visiting college class with a professor asking pointed questions that he wants his students to hear the answers for... the hope is that we can answer those.
And there are so many little things!
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| Proboscidae pelvis |
For example, I learned last summer about how you can tell whether a bone was exposed for an extended amount of time on the surface before it was buried and fossilized. This has to do with the cracks on the surface of the bone. Well, there are also little tiny parallel groves that can be formed when the bone has been buried and the ground above it has been walked on, particularly by animals with hooves, causing the grit to rub against the bone. For example, here is a proboscidae pelvis that was found in the formation directly below the ash layer (the ash layer is a formation known as the Ash Hollow formation, named for the area that settlers were able to rest at on their way out west after lowering their wagons down a cliff face, where the formation was first described.) This indicates that the species (probably one of the gomphotheres) were probably present during the ash fall but for some reason either left when it happened or survived it. You might be able to see the lines I'm talking about in the close up image. |
| See the lines? |
You see, unlike many geologic formations that can represent millions of years, the Ash Hollow formation represents a time span of maybe decades or centuries, if even that much. It is a layer of ash, which under the microscope still looks like little shards of glass (as modern ash does) which was deposited when the same hot spot that is now under Yellowstone went of about 11.83 million years ago. The hot spot was then in Idaho, and we can trace the composition of the rocks back there. The formation is also unusual because we can also date the exact layer that the fossils are in fairly accurately. We can also tell about how long the ash plagued the animals based on the age of the juvenile rhinos.
This specimen is really special. It is a female rhino that died from the ash while she was pregnant. Aside from the baby, you can tell males from females based on the size of the horns. This specimen is really neat though. The bone of the mother has Marie's disease, which is when new bone grows uncontrollably when an animal is dying from lung failure. This is still observed today though it is not well understood. However, the baby has no evidence of the disease, making a statement about how much the body is able to protect a baby in the womb.
So the animals found in the ash show signs of having died from suffocation due to the ash that was settling. It is thought that they preserved here and not other places in the same formation because this was a watering hole, which caused more animals to be present and more ash to collect, which allowed the animals to be better buried and preserved. There is remarkably little damage to the bones by scavenging despite the fact that several were obviously moved by scavengers, possibly because of the abundance of meat that was present (thus eliminating the need to get as much nutrition as possible from every bone.) There are remarkably few bones of predators or scavengers. While there would have been few of these, this may also be due to the fact that they were able to borrow to avoid breathing the ash as much as the grazers, who would have had to eat constantly. The scavengers could eat enough to be full and retreat back below the ash level. At least, that's one hypothesis.
The yellow flag in this picture marks the location of the first fossil that was found in the ash layer in the 70's. The man who discovered it still works at Ashfall and is one of our mentors for the internship, Dr. Michael R. Voorhies.So something that should be kept in mind about Ashfall: the ash didn't cause the extinction of these animals. After all, we still see rhinos and camels today, and the modern day camelids in Asia are likely descended from these. We know that they didn't go extinct because in the formation a few feet above the ash layer, we still find rhinos and other mammals that died in the ash. Species rebound after disaster.
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