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

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 spac e formed by lithospheric extension to be filled with sediments or wate r 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 km(2). Fo r an initially old continental lithosphere (thickness: 130 km), therma l equilibrium is reached in approximately 100 Ma for a basin of initia l width 100 km with a maximum beta-factor of 2.0. The duration of exte nsion for a given beta-factor affects the heat flow and subsidence. Fo r extension periods of 10 and 20 Ma, faster extension results in less subsidence and more prolonged high heat flow after the cessation of ex tension. 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 th ermal evolution of extensional basins. (C) 1998 Elsevier Science Ltd. All rights reserved.