Abstract

The fracture patterns exposed in the sedimentary rocks of the East Kaibab monocline, southern Utah and northern Arizona, were documented along three profiles perpendicular to the fold. The fractures were characterized on the basis of type (opening, closing, or shearing modes), geometry and spatial distribution. Four structural domains are defined from west to east across the monocline on the basis of recurrent fracture assemblages: (1) systematic joints at a high angle to the monocline trend and discontinuous joints at a high angle to the systematic set; (2) bedding plane faults and associated tail cracks; (3) major faults striking parallel to the fold axis and deformation band faults and (4) a systematic joint set parallel to the monocline and joints at a high angle to the systematic set. In addition to the systematic patterns, the Buckskin Gulch profile shows localization of deformation bands in dunes and compaction bands associated with deformation bands. The Kaibab monocline is considered an analog for folded reservoirs. The influence of the systematic fold related fractures and of various fault structures on fluid flow properties is inferred assuming flow is inhibited across deformation bands and slip planes and is enhanced along slip planes and joints.