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Day 6 - Sunday, September 28

This morning we rejoined the Friends of the Pleistocene for the last half day of the field trip. We made our first stop of the day at 8:30 AM at the Warrenton Drill Hole. Diana Baker (right) described several borehole cores collected near the south side of the ancestral Columbia River Valley that reflect sedimentation between 16,000 years ago and present day.

Diana Baker describes a deep borehole that was drilled in Warrenton, Oregon.

FOP participants at the Lewis River Marsh.

Curt Peterson talks about evidence of the last several Cascadia earthquake subsidence events.
Our final stop of the field trip came at 10:15 AM at the Lewis River Marsh, where we observed a cut bank containing evidence of the last several Cascadia earthquake subsidence events that have been identified by work done by Brian Atwater and others.

Scouting out the study area prior to collecting field data.

Curt, Mike, and Rebecca collect 100 MHz GPR lines.
This afternoon we began our field research at Slusher Lake, within Camp Rilea in Warrenton, OR. Our field research was focusing on finding a historic river outlet to the Pacific Ocean. Maps drawn by Lewis and Clark indicate that what is now Slusher Lake was historically the Clatsop River which had an outlet to the ocean. The outlet of the river is believed to have been filled in by sand, which stopped the flow of the Clatsop River forming Slusher Lake. Also, in the same area where the Clatsop River historically entered the ocean, maps drawn by Lewis and Clark indicated a small Clatsop Tribe encampment. Although our research was not focused on finding the village, we believed we were working in the area where the village might have existed.

We met with Curt Peterson and held a research briefing from noon to 1:00 PM in Koski Hall at Camp Rilea. After reviewing the Lewis and Clark maps and journal records, we decided to focus our work on the west side of Lake Slusher.

We began conducting field research in the afternoon. Data was collected using ground penetrating radar (GPR), GPS, and laser leveling equipment. We detected a distinct channel landform on the northwest side of Lake Slusher with the GPR equipment, and this landform was interpreted to represent the historic Clatsop River outlet originally mapped by Lewis and Clark. Hand auger samples revealed that as much as 6 m of Holocene sand had accumulated in this area since the construction of jetties at the mouth of the Columbia River in the early 1900s.

Harry and Jeremy collect 225 MHz GPR lines while Curt, Rebecca, and Mike collect 100 MHz GPR lines.

Mexican dinner at Mazatlans.
We ate at a Mexican restaurant near Warrenton called Mazatlans for dinner, and we spent the rest of the evening back at Camp Rilea going over Lewis and Clark’s journal and maps, trying to narrow down the location of the Clatsop Indian Village. We also processed our GPR and laser leveling data and printed out our GPR profiles. This information was used to determine where to focus our attention during the remainder of our field work tomorrow.

Based on Lewis and Clark’s map and journal records, we estimated the location of the Clatsop Indian village to be located around 300 m south of the historic Clatsop River outlet, and we concluded that the elevation of Lake Slusher was needed in order to estimate where the village is located relative to the west side of the lake.

Web page created by Michael Selb and Jeremy Treague

Web Site created by UWEC Geography 401 Class - Fall 2003