Physical modeling of evaporite-detached salients

Date
2006
Authors
Fox, Christine René Zúñiga
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Abstract

The use of scaled physical modeling of thin-skinned fold-and-thrust belts allows isolation of key parameters in the development of convex-toward-the-foreland folds and thrusts. Unlike salients formed in natural settings, scaled physical models can be monitored through time, with structures dissected and analyzed at the completion of the experiment. Conducting strain and displacement vector field analysis of individual model stages yields quantitative insight into the kinematics of salient development. I constructed twenty-one scaled physical models in order to study the processes leading to the formation of salients and extrapolate the models to natural examples. Thus, variation of model rheologies and boundary conditions test the influence of stratigraphic parameters on the formation of salients in thin-skinned fold-and-thrust deformation belts. The physical models created for this study reveal that the pre-collisional evaporitic décollement pinch-outs toward the foreland, lateral, and hinterland exert great influence on the degree of fold and thrust curvature across the salient, the presence of vertical axis rotation during salient formation, and the geometry of the structural trend line patterns of folds and thrusts within the salient. Brittle/viscous models showed two distinct patterns of fold curvature, local curvature near the décollement pinch-out and distributed curvature above the evaporitic décollement, dependent on the lateral and hinterland boundaries of the décollement. Fold axial traces initiated with localized curvature above the lateral pinch-out, while structures maintained linear axial traces above the central décollement layer in models with lateral boundaries perpendicular to convergence direction of a linear indenter. However, I found that vertical axis rotation of the folds and thrusts did occur. Conversely, fold axial traces initiated with distributed along strike curvature in models with a pre-collisional hinterland protruding décollement. Fold axial traces in viscous/viscous models initiated with localized or distributed along strike curvature that became more convex with progressive deformation. Vertical axis rotation also occurred in these models

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