FOLD TEST IN PALEOMAGNETISM: NEW APPROACHES AND REAPPRAISAL OF DATA

Abstract

It has been shown that any modification of the fold test leads to a definite conclusion about the magnetization nature if several basic assumptions are observed and the statistical test itself is correctly formulated. It has been demonstrated that the test based on comparison of concentration parameters (McElhinny, 1964) is controversial and may lead to erroneous conclusions. Two modifications of the fold test are proposed. The first one is based on the division of the bedding poles distribution into groups, calculation of the corresponding paleomagnetic group-means and their testing by the F distribution. This test is similar to that proposed by McFadden and Jones (1981), but can be used more widely. The second modification is based on correlations of unit bedding poles and paleomagnetic vectors and can be applied to any collection, provided the number of the unit vectors is 10 or more. All three tests were compared with the aid of simulated and real collections and it was shown that the latter two are more sensitive than the first one.