A FINITE-ELEMENT ALGORITHM FOR MODELLING THE SUBSIDENCE AND THERMAL HISTORY OF EXTENSIONAL BASINS

Abstract

We present a finite-element model for the prediction of the subsidence history and thermal evolution of extensional basins. The model takes into account the inhomogeneity of the lithosphere, and allows the space formed by lithospheric extension to be filled with sediments or water or both. Local isostatic compensation is assumed. The stability and accuracy of the algorithm are investigated. Time increments of 0.05-0.1 Ma are most appropriate for triangular elements of size 13 km2. For an initially old continental lithosphere (thickness: 130 km), thermal equilibrium is reached in approximately 100 Ma for a basin of initial width 100 km with a maximum β-factor of 2.0. The duration of extension for a given β-factor affects the heat flow and subsidence. For extension periods of 10 and 20 Ma, faster extension results in less subsidence and more prolonged high heat flow after the cessation of extension. If the basin is filled with sediments (as opposed to water), thermal blanketing effects are significant. The algorithm can be used to complement our understanding of the effects of thermal blanketing, lateral heat conduction, and sediment loading on the subsidence and thermal evolution of extensional basins.