AHLGREN, STEPHEN G. , University of Arizona, Dept. of Geosciences, Tucson, AZ

ABSTRACT: Three-Dimensional Structural Modeling of Foreland Basement Cored Uplifts, Southern Utah

The dramatic monoclines flanking Laramide-aged Colorado Plateau uplifts are generally thought to form over high angle basement faults whose origin and deep geometry are often unknown. The northern end of the Waterpocket Fold in southern Utah comprises two such uplifts, the Circle Cliffs and Miners Mountain uplifts. Related mesoscale deformation includes broadly distributed jointing and faulting as well as penetrative deformation banding localized within the transfer zone at Sheets Gulch.

The opposite vergence of the two uplifts and localized strain within the transfer zone suggests that the uplifts are cored by soft-linked, opposing basement fault zones. Although unexposed at the surface, the geometry of these fault zones may be inferred from down-plunge viewing and comprehensive, two-dimensional and three-dimensional structural modeling of the region using 2DMove and 3DMove. First, two-dimensional forward modeling based on balanced, serial cross sections will provide initial geometric and kinematic constraints and will serve as correlation points for three-dimensional modeling of the uplifts as fault propagation folds. Paleostress interpreted from inversion of surface data will be used to seed the computer models, and the validity of the models will be evaluated by comparing synthetic three-dimensional strain data recorded during forward modeling with regional strain data gleaned from field observations.

This integrative modeling will provide immediate insight into the applicability of current basement cored uplift models to this and other basement cored systems, and, in conjunction with mechanical testing of the Navajo Sandstone, may help to explain the enigmatic, penetrative deformation banding at Sheets Gulch.

AAPG Search and Discovery Article #90909©2000 AAPG Foundation Grants-in-Aid