Topographic controlled forcing of salt flow: Three-dimensional models of an active salt system, Canyonlands, Utah

Abstract

The grabens within Canyonlands, Utah, is an active salt system primarily driven by differential unloading due to incision of the Colorado River. However, many other conditions exist in the region that potentially influence regional deformation, including the gentle dip of the evaporite deposits, unconfined salt within the river canyon, weaknesses in the overburden, and topographic gradients on various scales. Three-dimensional numerical models were built to test the scale at which salt responds to these parameters individually and as a whole. Topography has a large influence on salt flow on both a regional and local scales and predicts the formation of existing structures in the region on consistent spatial scales without the influence of overburden weakening or salt geometry. Topography also has a large influence on the direction of salt flow, which acts to divert salt away from the canyon at the edge of the grabens and enhance salt flow within the grabens. Unconfined salt within the canyon regionally alters displacement rates and patterns, indicating a clear shift in strain before and after incision of the river into the Paradox Formation. On a local scale, there is a strong coupling between overburden weakening and salt flow patterns, where salt responds to individual structures and less to regional drivers. All these driving forces create an ensemble of feedback that alters the strain field and structural development through time.