Balanced Cross-Section Across The Southern Utah Overthrust Belt (Otb)

Abstract

Balanced cross-sections are offering the chance of better understanding of areas of complex geological structures that are insufficiently understood. Detailed field study and structural analysis by employing geometric balancing techniques is used to construct cross-sections along the major fold, the Virgin - Kanarra anticline, over a distance of 70 miles in the southern part of the Utah OTB. Two models were used to construct the cross sections: a) A computer modeling program, used to draw cross-sections in the mildly deformed areas, b) A' manual mathematical method, used in the strongly deformed areas. Four cross-sections are presented illustrating that: 1) The folds are caused by steps in a basal detachment thrust that links with a break thrust. The basal detachment in southwest Utah preferred the stratigraphic zones of relative weakness (shale, gypsum), but detachment also exist at high stratigraphic levels and complicate the fold shape in the highly deformed areas. 2) Along the major fold, the intensity of deformation is variable, with stronger activity in the middle (e.g. Spring Creek) and the northern portions and less deformation in the southern part.