Mechanical model for the tectonics of doubly vergent compressional orogens

Abstract

A mechanical model of crustal shortening and deformation driven by the relative convergence of rigid, underlying mantle plates explains many features of convergent orogens. Results based on numerical models and supported by sandbox models show that a Coulomb crustal layer subject to basal velocity boundary conditions corresponding to asymmetric detachment and subduction of the underlying mantle passes through three stages of orogenic growth: (1) block uplift bounded by step-up shear zones; (2) development of a low-taper wedge over the underthrusting mantle plate; and (3) development of a lowtaper wedge overlying the overthrusting mantle plate and verging in the opposite direction. When modified by isostasy, basal viscous flow, surface erosion and denudation, and sedimentation, the resultant model orogens exhibit a variety of styles with characteristics in common with small, rapidly denuded orogens, large orogens with plateaus and extensional characteristics, and active subduction margins with doubly vergent accretionary wedges and deformed fore-arc basins.

Orogeny and orography: The effects of erosion on the structure of mountain belts

“…These components are imbedded into a model of orogenesis which assumes that convergent orogens form by crustal detachment and shortening above a subducting substrate consisting of the lithospheric mantle and, in some cases, parts of the lower crust [Willett et al, 1993]. This mechanical model can explain the large-scale structure of mountain belts which are formed primarily by structural thickening as occurs in subduction forearcs [Silver and Reed, 1988 [Beaumont et al, 1996b].…”

Life cycle of the East Carpathian orogen: Erosion history of a doubly vergent critical wedge assessed by fission track thermochronology

“…The use of backstops with finite height resulted in significantly different wedge geometries [e.g., Malavieille, 1984;Byrne et al, 1993;Willet et al, 1993;Koons, 1989Koons, , 1990, although the deformation mechanism remained the same (Figure lb). The frontal part (or prowedge) still behaves as in the minimum tapered bulldozer model (Figure la), but differences occur to the rear above the tip of the backstop.…”

“…The frontal part (or prowedge) still behaves as in the minimum tapered bulldozer model (Figure la), but differences occur to the rear above the tip of the backstop. The tip of the backstop is a velocity discontinuum which in numerical simulations is termed a singularity point [Willet et al, 1993]. Above the singularity point forms an outer-arc-high, and in the same zone the stress regime flips orientation.…”

Erosion-driven uplift of the modern Central Alps

“…Dahlen et Suppe, 1988;Koons, 1989;Beaumont et al, 1992;Willett et al, 1993;Montgomery, 1994;Avouac and Burov, 1996;Burbank, 2002;Montgomery and Brandon, 2002;Hilley and Strecker, 2004;Whipple and Meade, 2004;Berger et al, 2008). The Central Alps (Fig.…”