Sample preparation for determination of comminution ages in lacustrine and marine sediments

Combined U isotopes and gas adsorption surface area analyses on two sediment samples from the Mediterranean Sea yield comminution ages up to 5 times older after sample treatment, which highlights the importance of a comprehensive removal of non-detrital matter from the bulk sediment composition. Moreover, gas sorption analysis allowed determining whether a fractal correction for calculation of the recoil fraction should be applied. Precise estimates of the recoil fraction are crucial for calculating the comminution ages, as it governs the loss of 234U from detrital matter. Samples analyzed in this study display Type II isotherms suggesting a non-porous or macroporous surface. Micro- and mesopores, which increase the surface area during gas adsorption analyses but do not contribute to the loss of 234U are absent. Thus, a fractal correction to account for micro- and mesopores is not required.