Problems With Net Tectonic Rotation for Dikes and Suggestions for Alternative Approaches

Abstract

The net tectonic rotation method is an alternative to paleomagnetic tilt corrections. The method was originally developed for sedimentary rocks and lavas, which have paleohorizontal indicators, but was later adapted for dikes by assuming that dikes intrude vertically. We conduct multiple numerical experiments that demonstrate geometric flaws in the net tectonic rotation method if dikes are not quite vertical prior to deformation. These flaws can impact the interpretations from the method, but the size of the impact depends on the original dike strike, dike dip, and the paleomagnetic reference direction. Our experiments show the worst behavior occurs for dikes that are approximately perpendicular to the reference declination. In addition, the results for dipping dikes of all initial strikes become increasingly distorted as the reference direction's inclination increases. Using data from two field areas in Cyprus and northern Iceland, we compare the application of net tectonic rotation to alternative techniques—relative comparisons and spatial regressions—that do not require an assumption of initially vertical dikes. We conclude with a list of questions that workers should answer prior to future application of net tectonic rotation to dikes.