DOMAIN ANALYSIS

A set of structural fabric elements that show unique character and consistency were chosen to define domains. The presence and type of thrusting, presence of low-angle normal faulting, presence of large-scale folding, and the intensity of high-angle faulting were selected to define exploration domains. In defining these structural domains it was important to keep in mind that more than one deformational event has affected the entire evaluation area, and that various structural levels are exposed at the surface as a result of deformation and erosion. The domain analysis relies on the assumption that surface structural style reflects the subsurface structural geometry of ranges, and the intervening basins filled by thick Cenozoic basin fill.

There are minor and local variations in structural styles within a domain, in part as a result of the rheology of the stratigraphic section deformed. An abundance of shales in a given stratigraphic section for instance, will result in relatively more abundant and disharmonic folding than sections with less shale. Variations in fold and fault orientations may have a bearing on kinematics, but commonly slight variations in a structural element are not reflecting major kinematic changes. Along with variations in a single structural fabric element, there is also a degree of variation between several fabric elements within a generally consistent domain. The intensity of high-angle faulting, folding and/or thrusting may vary to a minor degree within a given domain, with substantial variation or complete absence between defined domains.

A structural understanding on a domain scale allows the categorization of structural trap styles and assesses the potential of intact, non-breached hydrocarbon traps. Our belief is that subdomains of a smaller scale, say less than 5 square miles, are quite important when examining prospective areas to develop prospects. The detailed structural work necessary to define these areas involves months of field work and analysis, and should be undertaken on a prospect by prospect basis.

Eight major structural exploration domains are defined within the evaluation area. These include the Antler Thrust Domain, Golconda-Antler Thrust Domain, Golconda-Antler Thrust and Mesozoic Pluton Domain, Large-Scale Fold Domain, Low-Angle Normal Fault Domain, Simple Fault Block Domain, Northern Nevada Rift Domain, and Owyhee Plain Domain. Since these domains contain structural elements which are related to specific and multiple deformational events, several domains overlap one another. The domain outlines along with major high-angle basin bounding faults, lateral faults and lineaments are shown on the Structural Domains Overlay III. Each of the structural domains are discussed separately below. The domains are described in order from those characterized by the oldest deformational history to those with the youngest deformational history.