An updated inclination-only fold test for paleomagnetic studies

Abstract

A fold test is used to identify whether a component of the natural remanent magnetization (NRM) in rocks was acquired before, during, or after folding. When two sites belonging to different folds are unfolded, the so-called regional fold test, the test's outcome may be affected by local vertical-axis rotation between the sites. However, the tilt correction of NRM's inclination is immune to this effect. Therefore, an inclination-only fold test should be used to cross-check the conventional fold test. The mean inclination and precision parameters calculated by the Arason and Levi (2010) method are used here to update the inclination-only fold test. Paleomagnetic results of redbeds from the Sangdanlin area in the Tethyan Himalaya, which were affected by differential local rotations, illustrate the merit of this approach. We suggest that the combined use of conventional and inclination-only fold tests is required to evaluate paleomagnetic results from sampling sections that are potentially affected by local rotation.