Trishear Fault-Propagation Folding

Fault-propagation folds are produced by deformation that takes place just in front of the propagating fault. The fault tip propagates upsection, and the fold develops above the ramp with uniform fold angles.

 Figure: A) Kink-band model, B) Fold above thrust fault,

C) Fold above reverse fault, D) Fold above normal fault.

(Erslev 1991)

 

Fault-propagation fold hinges tighten and converge downward, forming a triangular zone of deformation that is concentrated on the tip of the propagating fault. This downward convergence of deformation is modeled as triangular shear zones. This lends the name to trishear fault-propagation folds.

Figure: Models of homogeneous and heterogeneous

fault-propagation trishear folds. A) Thrust faults,

B) Reverse faults, C) Normal faults. (Erslev 1991)

Understanding the geometry of fault-propagation folding is useful in creating balanced models of fold and thrust belts. Fault-propagation trishear folds are common in the Laramide structures of the Bighorn Basin in Wyoming.

All information from: Eric A. Erslev (1991) Trishear fault-propagation folding