The fold test in paleomagnetism as a parameter estimation problem

Most proposed fold test formulations use significance tests to try pre‐tilting and post‐tilting remanence hypotheses. We suggest that it is better to consider the fold test as a parameter estimation problem. Making the usual assumption that the distribution of remanence vectors was originally roughly parallel, we propose, using a monte carlo simulation technique, to estimate the amount of tectonic tilting at the time of magnetization along with a 95% confidence interval. If, for example, this confidence interval included 100% then one could not rule out pre‐tilting remanence. In the older terminology, the fold test is positive. The k‐ratio test of McElhinny [1964] is often said to be conservative in that if a study passes the k‐ratio test then it certainly passes a more rigorous test. We show with a typical counter‐example that this assertion is incorrect. Observational uncertainty of bedding directions is easily included in this formulation.