Characterization of the sedimentary fabrics in ornamental rocks by using GPR
In this study, the use of ground-penetrating radar for characterising ornamental sedimentary rocks was tested. Specifically, the ability of this non-invasive geophysical prospecting method to identify fabrics and textures in rocks was investigated. Blocks mined from quarries were analysed, and ornamental rocks with the same lithologies as other widely utilised ornamental rocks with a variety of sedimentary fabrics and textures were selected. Rocks with clastic brechoid, cross-laminated sparitic, massive or layered micritic, and laminar bindstone textures were analysed. Antennas that provided the maximum detail and a sufficient depth of penetration were used. The low electrical conductivity of carbonates permitted the use of high-frequency antennas (800 MHz and 1.6 GHz), which were useful in studying the entire thickness of a boulder (up to 2 m). The cross-laminations in the oolitic limestones, the laminar bindstones of travertines, the differentiation between massive and brecciated fabrics, and the massive and slaty fabrics of the micritic limestones were examined using these two frequencies. In micritic textures without discontinuities (neither sedimentary nor diagenetic), the radargrams could detect facies with few reflections (Crema Marfil). In addition to analysing fabrics and textures, the ground-penetrating radar measurements could identify anisotropy in these rocks, which makes ground-penetrating radar an effective tool for evaluating the mechanical state of a boulder prior to its cutting.