Saturday, March 29, 2008

Pleistocene Carbondale.






Kate's on the board of a local land trust (Green Earth). We worked with other volunteers on trail maintenance at one of GE's sites south of Carbondale. It's here:

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I don't think anybody's studied or described it, but on this border of the last glacial advance, and under strong influence from grade in the Mississippi River, now and in the late Pleistocene, we have a lot of what may be naturally incising channels. The gullies on the GE site are impressive. Very active headcuts.

These channels have some bedrock (shale and sandstone) control and I see what I call "Grover gravel," a mid or early-Pleistocene (I forget) formation with small, very well rounded quartz particles. I've collected a lot of these in St. Louis.

One photo (with Kate at right) shows a gully with a huge boulder; the bed appears to be clay residuum.

At the lower end of the GE site, a culvert at Kennedy Road controls hydraulics, and here's a photo of Kate (with JaJa the wonderdog in foreground) showing channel evolution; a bench on both sides of the channel.

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