Floodwaters with Muskrat (White River)
Originally uploaded by miss_distance
Note the creature swimming through the reflection?…. I am pretty sure it was a muskrat… swimming through the flooded fields. The White River’s channel lies *behind* that line of cottonwood trees (between the trees and the hillside).
Speaking of which: I’m still trying to nail down my stratigraphic ID-skills. At first I thought that the dark gray river-cut hillside in the distance was Pierre Shale, which would have been deposited as black marine mud sediments (from a great shallow inland sea that once covered this area). The Pierre Shale holds small fossils like ammonite shells, and even ancient sea-turtles and mosasaurs, which swam in the ancient seas. Pierre Shales are a glimpse back to the Late Cretaceous, so it lies before (under) the great extinction event known as the K/T boundary. Upon further reflection and reading — ! — I think this hillside is actually one of the northernmost examples of the Pine Ridge Escarpment, which runs all the way down into Nebraska. It looked darker than it really is at this time, because the sediments are damp. Still, escarpment is a landform term, and tells me more about the shape and history of the terrain, but I’m still foggy on the composition. From what I can tell, the Pine Ridge Escarpment is a drainage system feature. According to geomorphology professor Eric Clausen, the “Pine Ridge Escarpment is the south wall of what was a giant headcut that eroded west along the White River valley alignment to capture an immense southeast-oriented flood, including flood waters moving around the Black Hills south end.” This suggests to me that the far bank of the White River is revealing a cut-away view of blended sediments deposited in a wide fan (a gentle delta?) that once reached from the foothills of the eroding Rockies to the plains of the Dakotas. If this is the case, I’d guess that the sediments have been moved and worked and reworked by successive flooding events — even as they are in this week’s flooding. At any rate: I’ve been reading a book about the shift from the Eocene to the Oligocene, which has informed my re-reading of the cut bank of the White River. Perhaps an eminent geologist will stumble on my post one day, and they will write to me explaining exactly what the Pine Ridge side of the White River holds, in terms of sedimentary deposits, and ages? Until then, I’ll comfort myself with the words of Michael Polanyi who wrote about science and art (“The Creative Imagination”): But to know what to look for does not lead us to the power to find it. That power lies in the imagination.