The application of a viscoelastic lithosphere model to isostatic subsidence in backstripping

Abstract

A frequently applied simplifying assumption in basin modelling is that isostatic compensation is of local character and takes place simultaneously with the increase in sediment load. Using such a 1-D model may introduce errors in the estimated tectonic subsidence during backstripping. For some areas, or during parts of the basin evolution, a 1-D model may be a good approximation. In general, however, a more realistic model of the Earth's response to loading has to take into account the elastic stiffness and the viscous behaviour of the lithosphere. Such a model of the Earth's response to loading may have implications for correlations of gravity anomalies and tectonic events in a basin. Calculations carried out with a 2-D viscoelastic model in the Northern Viking Graben show that isostatic equilibrium is not achieved even 20-30 million years after sedimentation. The main purpose of this chapter is to quantify the effect of the lithosphere's elastic and viscous properties to estimate stretching factors, and consequently palaeoheat flow. The tectonic subsidence estimated from 1-D isostatic model may be underestimated by 15% when compared to a 2-D viscoelastic model constrained by published laboratory data on lithospheric viscosity and elasticity. -Authors