Modelling of stylolite geometries and stress scaling
Résumé
In this contribution we present numerical simulations of stylolite growth to decipher the effects of initial rock heterogeneity and stress on their morphology. We show that stylolite growth in a rock with a uniform grain size produces different patterns than stylolite growth in a rock with a bimodal grain size distribution. Strong pinning of large heterogeneities produce stylolite structures that are dominated by pronounced teeth, whereas a uniform grain size leads to spikes and a roughness that shows variable wavelengths. We compare the simulated stylolites with natural examples and show that the model can reproduce the real structures. In addition we show that strong pinning in the bimodal case can lead to a linear stylolite roughness growth in contrast to the non-linear growth of stylolites that develop from a uniform noise. In a set of 24 simulations we vary the main principle stress on the stylolite in order to test if our model can reproduce the analytically derived stress-scaling proposed by Schmittbuhl et al. (2004). We compare the calculated stresses with the applied stresses and show that the numerical model and the analytical solution are in good agreement. Our results strengthen the hypothesis that stylolites can be used as strain and stress gauges to estimate not only the orientation of paleo-stresses, but also their absolute values of formation stresses and amounts of compaction.
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