Abstract

Highly contorted siltstone strata of the Satanka Formation (Permian) are exposed in a stream bank northeast of Laramie, Wyo. Overlying the Satanka at this locality are Pleistocene fluviatile sediments (several lenses of sand and a bed of cobbles) which are also involved in the convolutions. In contrast with most previously described Pleistocene convolutions, those discussed herein show a pronounced directionality. The folds are asymmetrical with their steep limbs dipping southwest and many are overturned in the same direction. Although these features may have formed under periglacial conditions, a simple freeze-thaw mechanism is insufficient to account for their configuration. Deposition of the overlying load of cobbles on an unstable slope may well have induced the deformation.

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