Publications
Complex geometry: the projection and kinematics of 2D/3D bedding and slip systems, GSA Abstracts with Programs, volume 31, number 7 (1999 Annual Meeting), R. Ratliff, J. Geiser, P. Geiser, K. Ranzinger
The standard techniques for projecting bedding in 2D cross sections are intrinsically related to the techniques of section restoration and fault prediction: constant-thickness parallel geometry ('dip domain') defines the slip system used in flexural slip (bedlength balance) and slip line (constant fault displacement) methods, whereas similar geometry is the projection method compatible with vertical/oblique slip kinematic models. Although these techniques have yielded widespread success in determining and explaining subsurface contractional and extensional structures, they are based on rather crude approximations to natural rock geometries and their applications must be considered such as well. Examples of even roughly parallel dip domain geometry are rare at scales larger than a few meters. True similar geometries are typically limited to areas of passive bedding, i.e., where there is no competency contrast between layers; again, natural examples are restricted to scales smaller than a few meters, and these are usually at moderate to high metamorphic grade. Furthermore, whereas flexural slip is regarded as the appropriate restoration/modeling method for most contractional structures, the difficulty of extrapolating parallel geometry to 3D has, in part, restricted the description of true 3D projection and flexural slip restoration techniques. Indeed, many would argue that the typical limitation of vertical/oblique slip to extensional and flexural slip to contractional structures overly simplifies actual rock deformation, important distinctions when using restoration to predict fracture properties in hydrocarbon reservoirs. We here describe 'complex geometry', a new projection and kinematic model that provides a significantly more accurate representation of natural rock patterns in both 2D and 3D. Critical distinctions of complex geometry are that it is defined by one or more arbitrarily weighted 2D lines or 3D surfaces, and its constraining elements may, but need not, conform to constant-thickness parallel or similar geometries. The weightings control not only the proportional influence of the defining entities in projecting intermediate (interpolated) and extrapolated geometries, but also the relative contributions of parallel and similar style. Complex geometry provides a robust 2D/3D horizon and/or slip system projection method along with the heretofore unavailable ability to combine multiple constraining horizons and a mix of deformation models into a single kinematic entity.
