Core Samples

April 23, 2012

Art Bettis (Associate Professor, Geoscience), accompanied by Tiffany Adrain (Collections Manager, Geoscience), David Brenzel (Naturalist, Indian Creek Nature Center, Marion),, Sarah Horgen (Education Coordinator, UI Museum Natural History) and Holmes Semken (Professor Emeritus, Geoscience) met the landowner at his farm around 8:00 in the morning. The Giddings core rig that was towed from Iowa City was attached to the landowner’s tractor and pulled to the mammoth locality. One core (16 feet) was collected about 20 yards south of the outcrop with the mammoth remains on the terrace immediately above the mammoth. A second core (20 feet) was collected about 40 m further south from the outcrop on the next higher terrace. Art reports that both cores transgressed the unit containing the mammoth and bottomed in sand immediately below that unit.

After coring, we hatched an initial excavation plan with the landowner for our next trip. The mammoth bed lies on saturated gravel and beside a small streamlet that pours into the landowner’s excavation. Flooding is enhanced by a partial dam created when the specimens recovered to date were removed. The landowner says that there are mammoth-bearing sediments (including ribs) at the base of this dam and it is capped by back dirt from his excavation. The dam needs to be removed to facilitate drainage and recover the remaining specimens. The back dirt also needs to be screened because smaller bones have been recovered from the spoil. There is only one acceptable way to throw the dirt in the dam out and that is up (a long throw) to avoid impeding flow out of the pit downstream. Also, the streamlet and the creek are crystal clear and we do not want to muck it up. For those who have not seen the location, it is beautiful as well as pristine with the clear rippling creek. The landowner has a backhoe but it will not reach the target area. He can get close. Therefore, the plan is to get about 10 volunteers to shovel into the extended bucket of the backhoe and lift it to a dry screening area on the terrace. This should be fun for the volunteers as there will be bones at the bottom and probably in the fill. Hopefully, the site will drain after this operation. If not, an ADS system might be rigged. Pumps would be a last resort. As at the Tarkio, plans can change as we work.

Art has an undergraduate who is interested in describing the two cores. This will really facilitate our working knowledge at the site. Also, there is lots of organic material, good for dates and paleobotanical studies. I did not see any snails but who knows.

Dick Baker has looked at the grab sample of mammoth-bearing sediments that Art collected during our first visit and reports lots of spruce (probably both black & white), larch needles, probably fir, a violet seed and raspberry seed fragments along with a couple of unknowns. Pollen is undoubtedly present.

Dave Campbell (Adjunct Professor, Geoscience) is interested in exploring the site with radar. The bone bed is too deep for the system that he uses but Glenn Story (Associate Professor, Classics, Anthropology) and Frank Weirich (Associate Professor, Geoscience) may have a bigger antenna. He will investigate.

We are looking at weekends in early June for the first excavation.

Andy’s story appeared the next day in the Oskaloosa Herald and can be viewed here.

Holmes Semken, April 28, 2012