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.