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Volunteers haul clay, mud and rock from a pit while another group sieves the mixture looking for fossilized remnants.
October 04, 2011
KINGS VALLEY -- Seen a sloth or camel in the area lately?
Not likely, unless you were at a zoo or farm.
But in the relatively recent past -- geologically speaking -- those animals in somewhat familiar forms were common in North America.
The proof was excavated from the ground underneath a farm field in Kings Valley the weekend of Sept. 24-25.
The dig near the Polk-Benton county line was overseen by Bill Orr, retired University of Oregon professor, and Mike Full, an avocational paleontologist with McMinnville's Yamhill River Pleistocene Project. Linfield College biology professor John Syring and his evolutionary biology students joined the dig, along with several other volunteers.
Fossils on the farm site were discovered in the early 1990s by owner Ted Leonard, who was planning to dig a water hole in the field. When he started digging, he discovered bones.
"I knew it was something prehistoric," Leonard said.
He called experts at Oregon State University, who started work on the site in the early 1990s.
In the last two years, Orr and Full have resumed the digs, which happen each summer after the field is harvested, but still during the dry season.
In typical Oregon "dry season" fashion, the dig was interrupted by rain. Sept. 24 was spectacular - hot even - but Sunday, Sept. 25, was cooler and damp. A 15-minute downpour even sent volunteers running for shelter once on Sunday morning.
No matter, though, the dig was soggy to begin with.
"Can someone get me some more goop, please?!" Linfield biology major Leah Rensel called out after lunch on Sunday.
She was referring to the buckets of a sludgy rock and clay mixture being dug out of the pit where the fossils have rested for thousands of years. Rensel's job on the afternoon was to sift through the "goop" looking for 12,000-year-old mega fauna bones and other remnants.
The term "mega fauna" refers to the size of the animals, which were simply enormous. The extinct ground sloths the group was digging up would have been a terrifying sight. They stood 6-feet tall at the shoulder, weighed about 1« tons and had foot-long claws.
Fossilized sloths leave calling cards -- small bone fragments that were once embedded in their skin called ossicles. Ossicle shapes are unique to each species of sloth, Orr said, making identification easy.
Most of what was found over the weekend consisted of the primitive body armor.
"It's similar to a coat of (chain) mail," Orr said.
The "cool" discoveries, according to Full, were a sloth tooth and cheek bone.
The fossils will become part of the Thomas Condon Fossil Collection at the Museum of Natural and Cultural History at the University of Oregon.
Mike Full, a paleontologist with the Yamhill River Pleistocene Project, holds the tooth of a Harlan's Ground Sloth dug near Kings Valley on Sept. 25.
While exciting to those involved, taking 12,000-year-old fossils out of the ground is difficult, slow work.
"It's like putting together a puzzle," Orr said of the delicate and lengthy process. "It takes a lot of people to do it."
The dig had people in the pit shoveling and scooping material into buckets and hauling it up a set of wooden stairs to a different group of volunteers, who would pick through it.
Using a large tub of water and sieves capturing any material 1/8 of an inch or larger, the volunteers rinsed the material, separating clay from rock and rock from fossilized sloth bones, ossicles and hair.
Leah Rensel (bottom left), a Linfield College biology major, sieves a clay-and-rock mixture in a huge tub of water as several other volunteers do the same Sunday, Sept. 25, in a field near Kings Valley.
"Hair is pretty neat, because it usually decomposes," said geologist Sheila Alfsen, a teacher at Chemeketa Community College.
Volunteers found what they believed might be a strand with an intact root, which may yield DNA.
The Kings Valley discovery, and other sites like it, are critical because fossil records for land animals are weak, Alfsen said.
Conditions have to be perfect to prevent decay and scavenging from destroying anything left behind.
"The only way that you find a fossil is if it is buried quickly and kept away from oxygen and scavengers," Alsfen said.
The site, and those like it, could eventually help solve mysteries surrounding Ice Age mega fauna, such as why they were so large and why they died out so suddenly 12,000 to 10,000 years ago.
Despite the heat, rain and thick layer of the bluish, grayish, clay and mud mixture covering everyone from head to toe, the dig was a revelation for the students.
"It's a different side of a dig than the cliched image of people with paint brushes cleaning off a perfectly laid out skeleton," Linfield student Rebecca Soderlind said. "It's definitely fun to be included in something so exciting and rare."
Syringsaid this is the first time his students were able to join the dig. He said it was an opportunity to work directly with fossils, an experience often limited to trips to a museum.
"This is a chance to work with fossils and bring material back to study," he said.
When the dig ended, the group took down its equipment and returned the pit to its own devices. Within days it was filled with water, preserving the fossils. Once again, the field looked like any other, leaving no clues to its ancient contents.
For the scientists and paleontology enthusiasts involved, that is the thrilling part of making the kind of discoveries Leonard did two decades ago.
"There's a whole history underneath your feet that you don't even know about," Alfsen said.