Application of younging tables to the construction of relative deformation histories—1: Fracture systems

For a collection of age relationships there are several possible histories. Younging tables provide a simple and direct method with which all valid deformation histories can be identified. The application of this technique to fracture systems is illustrated using two case studies. These examples demonstrate how unobserved relationships, synchronous structures, and fractures that appear in more than one stage of a deformation history can be dealt with using younging tables. Suggestions are made for the presentation of relative deformation histories that highlight ambiguities and convey a visual impression of the confidence that may be placed on a particular history. Application of the approach to the analysis of grain fragmentation has identified a range of multi-stage deformation histories. All of these histories involve, to a greater or lesser extent, the operation of extension fractures, shear fractures, linked shear fractures and extension fractures, and several sets of synchronous extension fractures. Analysis of an exposed fracture system using younging tables has raised the possibility of the simultaneous growth of two sets of orthogonal extension fractures with the implication that the scale of stress homogeneity may be only a few metres.