Insight into collision zone dynamics from topography: numerical modelling results and observations

A D Bottrill,J Van Hunen,M B Allen

doi:10.5194/se-3-387-2012

Abstract

Abstract. Dynamic models of subduction and continental collision are used to predict dynamic topography changes on the overriding plate. The modelling results show a distinct evolution of topography on the overriding plate, during subduction, continental collision and slab break-off. A prominent topographic feature is a temporary (few Myrs) basin on the overriding plate after initial collision. This "collisional mantle dynamic basin" (CMDB) is caused by slab steepening drawing, material away from the base of the overriding plate. Also, during this initial collision phase, surface uplift is predicted on the overriding plate between the suture zone and the CMDB, due to the subduction of buoyant continental material and its isostatic compensation. After slab detachment, redistribution of stresses and underplating of the overriding plate cause the uplift to spread further into the overriding plate. This topographic evolution fits the stratigraphy found on the overriding plate of the Arabia-Eurasia collision zone in Iran and south east Turkey. The sedimentary record from the overriding plate contains Upper Oligocene-Lower Miocene marine carbonates deposited between terrestrial clastic sedimentary rocks, in units such as the Qom Formation and its lateral equivalents. This stratigraphy shows that during the Late Oligocene–Early Miocene the surface of the overriding plate sank below sea level before rising back above sea level, without major compressional deformation recorded in the same area. Our modelled topography changes fit well with this observed uplift and subsidence.

Highlights

In this study we aim to look at the evolution through time of topography on the overriding plate at a collision zone. 2-D numerical models of lithosphere-mantle interactions at subduction and continental collision zones are used
The forces that influence topography can be broadly categorised into isostatic forces, from thermal and crustal buoyancy, flexure forces associated with the lithosphere, crustal strength as well as stresses imposed at the base of lithosphere due to mantle dynamics
This section describes how model dynamics are reflected in the surface topography and how these topographic features evolve over time

Summary

Introduction

In this study we aim to look at the evolution through time of topography on the overriding plate at a collision zone. 2-D numerical models of lithosphere-mantle interactions at subduction and continental collision zones are used. Many modelling studies have found a change in the dynamics of mantle flow during the transition between subduction, collision, and oceanic slab break-off (Gerya et al, 2004; Andrews and Billen, 2009; Duretz et al, 2011). These changes in flow in the mantle would be expected to affect the topography generated due to changes in the stresses at the base of the lithosphere (Faccenna and Becker, 2010)

Objectives

Methods

Results

Discussion

Conclusion