Buckling experiments on intersecting fold patterns

Abstract

Deformation tests with soft materials, such as modelling clay and putty, indicate that in the case of synchronous cross-folds, a complicated pattern of diversely oriented folds is developed, with large fold arcuations, virgations, domes, and basins. In the case of superposed folding, the types of folds which form in the second generation are principally of two types. Of these, the first type is always much smaller than are folds of the first generation, while the second type is roughly of the same order of magnitude as are first-generation folds. The experiments suggest that, in buckling-folds, large arcuations of fold trend are generally produced by coalescence of folds formed at the same time, rather than by buckling of a pre-existing system of folds. Successive compressions at low angles to each other failed to form cross-folds. Since successive compressions at high angles are more likely to be recognized as cross-folds than are those at low angles, orthogonal relationship of two fold trends must not be taken as a criterion for synchronous deformation.