| Abundant exposures of clastic dikes in Badlands National Park, SD, provide an excellent opportunity to use modern GIS techniques as a tool for characterizing fracture networks. Over 150 dikes were mapped with high-resolution GPS as well as in 1-2 m resolution air photos and satellite images. During mapping I simultaneously collected data on attributes such as dike aperture, internal structures, grain size of dike material, and cross-cutting relations. I analyzed the spatial distribution of all of these attributes, as well as dike length, orientation, and distribution of dikes throughout the roughly 2 square kilometer study area.;In conjunction with the GIS map, I conducted a series of mechanical models in Poly 3D (computer application that employs the boundary element method to calculate displacements, stresses and strains) to evaluate the plausibility of known local normal faults triggering the formation of some or all of the dikes in the study area. In these models, fault attributes such as trace length, dip angle, penetration depth, and regional strain direction were varied. Known fault orientations were used to analyze the effect of the various fault attributes on the local stress field in the area where the dikes were observed.;Using similar data, geologists can constrain important variables necessary to construct quality reservoir models for clastic injectite complexes. These techniques could also be adapted for fracture network analysis where dikes are not present. |
