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3 August 2018

Friday fold: a recumbent set of turbidites in the Black Hills

Today we feature a famous recumbent, chevron anticline near Hill City, South Dakota has been featured as a Friday Fold or not, but thought I would give it a go. The rocks are Proterozoic metagreywacke turbidites with 70 complete or partial Bouma sequences. This is believed to be a late (D4) fold in the Black Hills related to upward doming associated with the emplacement of the Harney Peak Granite, which …

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4 July 2012

Plane views: Powder River Basin and Black Hills

Happy fourth of July! Here’s two scenes that are emblematic of America, as seen from my airplane window last March flying from Reno to Minneapolis. Here’s the scene in the central Powder River Basin of eastern Wyoming: If you zoom in, you’ll see what caught my eye – regular rectangular excavations into the surface. These are strip mining operations for coal laid down in the Paleogene period of geologic time. …

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11 November 2010

Microfaults-a-million

I got to Pittsburgh around 1:30pm yesterday, which meant I had several free hours before the opening reception for new Fine Fellows. I took a bunch of photos of the exhibits there, but my traveling laptop doesn’t have the image processing software that I usually employ to resize these things, so for now I’ll just share this one. It’s a sandstone from South Dakota, age unknown, which shows beautiful parallel …

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