Anisotropic scaling of tectonic stylolites: A fossilized signature of the stress field?

Abstract

Vertical stylolites are pressure solution features, which are considered to be caused by horizontal tectonic loading, with the largest principal compressive stress being (sub‐)parallel to the Earth's surface. In the present study we analyze the roughness of such tectonic stylolites from two tectonic settings in southern Germany and northeastern Spain, aiming to investigate their scaling properties with respect to the stress during formation. High‐resolution laser profilometry was carried out on opened stylolite surfaces of nine samples. These data sets were then analyzed using one‐ and two‐dimensional Fourier power spectral approaches. We found that tectonic stylolites show two self‐affine scaling regimes separated by a distinct crossover length (L), as known for bedding parallel stylolites. In addition, tectonic stylolites exhibit a clear in‐plane scaling anisotropy that modifies L. Since the largest and smallest crossover lengths are oriented with the sample vertical and horizontal directions (i.e., σ2 and σ3) and L is a function of the stress field during formation as analytically predicted, we conclude that the scaling anisotropy of tectonic stylolites is possibly a function of the stress field. Knowledge of this crossover‐length anisotropy would enable the reconstruction of the full three‐dimensional stress tensor if independent constraints of the depth of formation can be obtained.