Finite-element modelling of Tertiary paleostress fields in the eastern part of the Tajo Basin (central Spain)

Three subsequent Tertiary paleostress fields that are deduced from fault-sl ip data for the eastern part of the Tajo Basin are analyzed by finite-eleme nt studies. The modelling results show that maximum horizontal stresses (S- Hmax) are mainly controlled by the geometry of the model limits and the bou ndary conditions applied. The models are used to test two hypotheses on the origin of the Altomira Range. A local stress field responsible for its for mation ('Altomira') can be modelled successfully by superposition in time a nd place of two major paleostress fields ('Iberian' and 'Guadarrama'). Stre ss trajectories have been modelled with respect to a homogeneous cover and heterogeneous basement to investigate the role of rheological contrasts bet ween different basement blocks on the orientation of the stress field. Resu lts of this kind of modelling suggest a mechanical decoupling between the c over and the basement, especially for the 'Altomira' paleostress field. (C) 1998 Elsevier Science B.V. All rights reserved.