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. Ma king the usual assumption that the distribution of remanence vectors w as originally roughly parallel, we propose, using a monte carlo simula tion technique, to estimate the amount of tectonic tilting at the time of magnetization along with a 95% confidence interval. If, for exampl e, this confidence interval included 100% then one could not rule out pre-tilting remanence. In the older terminology, the fold test is posi tive. The k-ratio test of McElhinny [1964] is often said to be conserv ative in that if a study passes the k-ratio test then it certainly pas ses a more rigorous test. We show with a typical counter-example that this assertion is incorrect. Observational uncertainty of bedding dire ctions is easily included in this formulation.