Using the Schmidt hammer on folds: An example from the Cantabrian Zone (NW Iberian Peninsula)

Abstract

The Schmidt hammer, widely used in Engineering Geology, has also been used in Structural Geology as a tool to quantify the mechanical properties of rocks affected by different structures and the damage caused to rocks by fracturing. However, how the impact resistance of rocks (rebound) varies in layers located in different positions of a fold has never been tested. Here, the Schmidt hammer is used to quantify this parameter in a syncline involving a Carboniferous carbonate sequence located in the Cantabrian Zone, the foreland fold-and-thrust belt of the Variscan orogen in western Iberia. The variations in the Schmidt-hammer rebound value along a folded layer are consistent with other indicators such as variations of dip and thickness. These findings have also implications on obtaining representative rebound values of stratigraphic units, and on deriving parameters such as the uniaxial compressive strength and the Young modulus from the Schmidt-hammer rebound values applied to folded regions.