Mapping of major fold closures from minor structures: A review of the relative merits of vergence, facing and S-Z concepts

The relatively new method of mapping minor structures in terms of vergence is compared with the more orthodox S-Z mapping technique. The vergenz-concept is not in all cases an unambiguously preferable alternative over the S-Z system, as has recently been suggested by Bell (1981). Both concepts have their relative benefits, dependent on the orientation of the fold axes, fold cylindricity and whether or not refolding is coaxial. The early concept of structural facing is preferable to either the S-Z or vergence systems of classification to determine major early fold closures in non-coaxially refolded rocks. Recommendations are made as to where the use of the vergence, facing and the S-Z concepts of mapping are most effective.