A thermo-mechanical model of continental lithosphere

Abstract

An understanding of the mechanical response of the continental lithosphere to vertical surface loading is crucial when considering geodynamic processes such as intraplate basin formation, postglacial rebound or mountain building. Previous models of the mechanical behaviour of the lithosphere, which are more successful in oceanic than in continental regions, have used specific isotherms to delineate an effectively elastic zone of the lithosphere and result in mathematically convenient descriptions of mechanical behaviour. Heat flow and lithosphere flexure data for continents, however, suggest that this relationship is more complex, which can be demonstrated by numerical modelling of the loading of a heterogeneous visco-elastic lithosphere with temperature-dependent viscosity. Viscous stress relaxation in the lower and hotter section of the lithosphere results in a region of stress concentration dependent on the thermal state of the lithosphere, its structure and the time since loading. Here we present initial numerical models, based on a relatively simple steady-state thermal model constrained by present-day heat flow, which explain observations of continental flexure except in regions which have experienced a long or complex thermal history since loading.