UNDERSTANDING THE INFLUENCE OF TAPER ANGLE ON FLUID SYSTEM EVOLUTION IN AN OROGENIC WEDGE

Fluid system evolution within an active orogenic wedge is governed by dynamic interactions between topography driven fluid flow, thermally induced fluid density gradients, prograde dehydration reactions, internal geologic structure, and regional tectonic compression. Despite this complexity, it has become widely accepted that topography is the primary driving potential responsible for basin scale fluid migration within the upper 7 to 10 km of an orogenic wedge. Nevertheless, there has been little effort to isolate the role of topographic slope within fluid regimes of contractional orogenic wedges. In response, we have developed a numerical modeling experiment designed to isolate for the effects of topographic slope on fluid system evolution within a critically tapering orogenic wedge. Three models are presented with critical taper angles of 10°, 4°, and 2°, and fluid flow is simulated within each model scenario for 200,000 years. In order to isolate for the effects of topographic slope, the internal wedge structure is isotropic and homogeneous, the basal detachment slope within each model is 1°, and the continental thermal gradient is neglected. In assessing the influence of topographic slope on meteoric water penetration and mixing with connate waters, a constant rate infiltration is applied at the free surface. Analysis of fluid mass flux within each model after 200,000 years of simulation time provides a first-order constraint on the contribution of topographic slope to fluid flux in real world scenarios. Similarly, analyzing fluid flux magnitude over time within each model constrains the theoretical threshold at which orogenic fluid systems may achieve a steady flow regime.