Extrapolation of depositional geometries of the Menorcan Miocene carbonate ramp with ground-penetrating radar

Abstract

The Tortonian carbonate ramp of Menorca was previously studied on the basis of outcrops along sea-cliff outcrops. These sea cliffs, in combination with inland water wells, are the basis for a facies model for the reconstruction of the internal architecture and for characterizing the internal heterogeneities of this carbonate platform. How- ever, any such three-dimensional reconstruction is generally limited by the given geometrical arrangement of the two- dimensional outcrops and the uncertainties of correlation with the one-dimensional wells. Here, ground-penetrating radar (GPR) has been employed in order to test and refine the depositional model. Although GPR is well known for being an excellent tool for high-resolution underground studies of sedimentary systems, the application for studying carbonate rocks is still far from routine. The reason for this discrepancy is two-fold: the minor mineralogical contrast between lithologies in carbonate rocks results in subtle reflections, and, even more important, the porosity structure in carbonates is thoroughly and repeatedly changed during diagenesis, commonly across the different facies, leading to problems in predictability of the petrophysical properties. The study of the Menorcan carbonate ramp with large dis- tance-deep penetration GPR sections demonstrates that in spite of these difficulties, GPR is a valuable tool for extrapolating information from outcrops and wells. It is useful for characterizing heterogeneities larger than outcrop scale.