The Helena salient is an arcuate curve in the southwest Montana fold and thrust belt, characterized by thin-skinned folding and thrusting. Ages from volcanic sills imply that deformation in the region began 77 million years ago during the Late Cretaceous (Harlan et al., 2008). This study investigates the nature of curvature associated with this salient using paleomagnetic techniques. Carbonate rocks of the Mississippian Madison Group were sampled from 24 sites across three folds: the Devil's...