The interpretation of stretching lineations in multiply deformed terranes: An example from the Hualapai Mountains, Arizona, USA

Stretching lineations are commonly assumed to be genetically related to the foliation plane in which they occur and are generally interpreted to represent the finite elongation direction, or tectonic transport direction in highly strained rocks. In multiply deformed terranes, however, lineations may be reoriented rendering their interpretation less straightforward. This situation could lead to misinterpretation of the kinematics or strain signature of the second event. An example from the Hualapai Mountains, Arizona, shows that, where two discrete deformational events occurred under similar physical conditions, an early L₁ lineation developed on S₁ could be misinterpreted as an L₂ lineation developed on S₂. Here, a gently dipping S₁ fabric was reoriented by folding into a steeply dipping composite S₁/S₂ fabric. In areas of little D₂ overprint, the L₁ lineation is essentially down dip. F₂ folding of L₁ resulted in reorientation of the lineations to very shallow rakes. D₁ fabrics are exposed only in extremely limited areas due to nearly complete overprinting by D₂ structures. Therefore, unless thorough field mapping reveals the local presence of D₁ structures, it would be easy to infer mistakenly that the L₁ lineation seen on the widespread S₂ foliation formed during D₂ thereby leading to an incorrect interpretation of the strain signature and kinematics of the second event.