Numerical Modelling of Thermal Effects of Compressional Faulting and Denudation: the Sierra de Guadarrama (Central Spain)

We present a two-dimensional numerical model for the thermal response on lithopsheric shortening. The model is fully time-dependent, and includes the effects of alternating fault activation in the upper crust. Furthermore, any denudation-history can be imposed, implying that erosion and uplift can be studied as independent factors. The model is used to investigate possible tectonic scenarios for the Cenozoic development of the Sierra de Guadarrama in the Spanish Central System. In earlier work, based on fission track analysis, it was suggested that the southernmost part of the present-day Sierra de Guadarrama was part of the Madrid Basin during the Paleogene. This would explain coeval Paleogene heating of samples in the southernmost fault-block, and cooling of samples more to the north. We use T-t curves obtained from fission-track analysis as constraints for our modelling, and test whether this scenario produces enough heating in the southernmost block to explain these data. Furthermore, we focus on the Pliocene accelerated cooling observed in all the samples, aiming to find out whether this reflects a Pliocene phase of uplift, or rather a Miocene phase of uplift followed by Pliocene denudation. The modelling demonstrates that uplift in the absence of erosion can cause already more than 50% of the total cooling of a rock sample after complete denudation. Our results indicate that the scenario suggested above cannot explain the amount of Paleogene heating observed in the rocksamples. Extra strike slip deformation seems to have been important. The only scenarios resulting in Pliocene cooling as observed in the SdG are those incorporating uplift during this timespan.