From spatial variation of fracture patterns to fold kinematics: A geomechanical approach

[1] A vertical, compression-parallel joint set apparently formed at Sheep Mountain Anticline (SMA) during the early Laramide orogeny, prior to significant folding. Field data indicate that these joints occur in fewer locations in the forelimb than in the hinge and backlimb. Using three-dimensional elastic dislocation models, we show that early slip along an underlying thrust fault can locally perturb the surrounding stress field, inhibiting joint formation above the fault. Thus, we are able to constrain the forelimb kinematics finding that the forelimb was originally located in the hangingwall, above the thrust fault. Furthermore the mode of folding at SMA is constrained: the anticline developed with a fixed hinge and rotating limbs, while the underlying basement rocks deformed internally.