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3 September 2010
Friday fold: tight syncline in Montana
This fold is located on Highway 287, north of Wolf Creek, Montana. Annotated version: As with last week’s Friday Fold, this fold owes its existence to (a) deposition of sandstone and shale in the Western Interior Seaway, and (b) deformation under a giant thrust sheet during the thin-skinned compressional tectonics of the Sevier Orogeny. In this case, we’re south of the Lewis Thrust, and the local equivalent is called the …