Go Back



Pinnate fractures - (also called feather joints), occur in the vicinity of the fault but at an angle to it (V&M Fig. 7.17). The acute angle between the feather joints and the fault points in the direction of relative movement of the block on which it lies. They may form before or during the faulting process and have a relationship to the regional stress field that is the same as that for en echelon extension fractures.


radial joints normal fault patterns associated with domal structures (e.g. Gulf Coast salt domes).


Sheeting joints a) Joints that are subhorizontal or parallel to topographic surfaces. b) Typically form in massive igneous rocks (such as granite) that do not have bedding or other planar anisotropies. c) Unlike unroofing joints, these joints form as a result of subviertical tensional stresses that are believed to be a result of residual stresses in the rock. d) Residual stress can develop due to differing thermal properties of adjacent rocks resulting in differential expansion or contraction.