Four members of the sloth team, David Brenzel, Lynette Stephenson, Holmes Semken and Kathy Woida (geologist, U. S. Department Agriculture, Des Moines), arrived in Shenandoah Sunday evening, Nov.2, with the objective of probing exposed blue-grey clay exposures uncovered by the excavator on the south bank of the West Tarkio for bone and to remove overburden and recover potential skull fragments exposed in the north bank of the excavation. Kathy, who has been working on the geology of the West Tarkio, also would evaluate excavation strategy based on her knowledge of the area geology. Unfortunately, five inches of rain fell over the two days prior to the site visit (Nov. 3) and the entire working area was underwater. The Tarkio stretched from the north bank to the south bank of the diversion channel.
Kathy did take a few grab samples from the south bank with the soil probe and identified till (an over-consolidated, high-plasticity, silty-clay loam with pebbles) within 4 ft of the surface. (According to Kathy, West Tarkio Creek is incised down to till at places north of the site in Page Co.) Although the sample was 30-40 meters from the rib-cage area, this reinforces the idea that the bones occupy a fairly small stratigraphic interval. This is reinforced by micromammal samples taken for water screening from the rib cage area. The 20 pound sample associated with the sloth remains produced a frog phalange and no rock clasts. The 30 pound sample from the unit underlying the bone-bearing unit was barren but did contain a few small, fairly rounded pebbles.
After an hour at the site Tuesday morning, the crew returned to Shenandoah with the hope of viewing mammoth remains recovered from a sand pit by the McLaren Sterling Construction Company some years ago. We were a day early for our appointment and the owners were at work sites elsewhere. We agreed, via cell phone, to view the specimens on our next trip, the date to be arranged. The next rip is tentatively planned circa November 24.
Holmes A. Semken November 7, 2003