Stratigraphic Section at Indian Creek, Lincoln County, WA
October 10, 2017
Section is located along Indian Creek Road just upstream from the confluence of Indian Creek and Hawk Creek. Hawk Creek Campground on Lake Roosevelt is less than a mile away.
I was given permission to describe a section through Glacial Lake Columbia/Missoula flood sediments by the M&L Construction foreman whose crew was installing erosion control matting along a nearly 1km long cut face at Indian Creek (Hawk Creek), Lincoln County, WA. The smooth slope was cut back to some 35 degrees, which is just barely walkable. I had only 40 minutes to complete the work shown above. The vertical section is approximately 30m high. I could not make measurements, so the thicknesses shown are relative. Only three units were used: "Sand" (gray, outburst flood beds), "Sand-Silt" (tan-brown, waning flood deposition), and "Clay" (green-gray-brown, lacustrine deposition). Rip-ups (RU) and soft sediment deformation features (SSD) were also noted.
Take away lessons for visiting geologists: 24 outburst flood beds interrupt more or less continuous lacustrine sedimentation during this phase of Glacial Lake Columbia. Soft sediment deformation comes in two forms here: syn-flood deformation and deformation related to coherent, rotational landslide blocks.
The 24 flood beds preserved in the section at Indian Creek validates Eugene Kiver's hunch that "at least 27 floods" entered Glacial Lake Columbia (Kiver et al. in Baker et al. 1991, p. 241). My hasty stratigraphic column above represents the only "continuous section of alternating flood and normal glacial lake sedimentation...exposed in the low-level Lake Columbia terrace" (p. 241) recorded to date.