Using dual-energy CT to discriminate sediment facies in a varved sequence 

The attenuation of X-ray is influenced by the density (electron density, ρe) and the elemental composition (effective atomic number, Zeff) of the object being imaged. The incident X-ray beams energy controls the relative importance of these two properties in the resulting X-ray attenuation. Yet, dual-energy X-ray computed tomography, or using two incident X-ray beams of different energy, has been used in medical sciences to distinguish the different compounds within a sample based on their density (electron density, ρe) and elemental composition (effective atomic number, Zeff).An innovative approach, i.e., the stoichiometric calibration for dual-energy X-ray computed tomography, was already successfully implemented to identify single and homogeneous minerals easily and non-destructively. It is here applied for the first time to a varved sequence with three distinct facies. The output of dual-energy X-ray computed tomography was compared against elemental geochemistry obtained at the same resolution using a micro-XRF core scanner. The three individual facies can be successfully differentiated using dual-energy X-ray computed tomography because their range of ρe and Zeff values allow their discrimination. Correlations with elemental geochemistry are also discussed but are less conclusive, probably because of variations in grain size and porosity, and because these high-resolution analyses were not performed at the exact same location. We discuss the limitations when using dual-energy X-ray computed tomography on sediments but also demonstrates its potential to quantitatively study sediment cores in a non-destructive way.This presentation is based on https://doi.org/10.1002/dep2.27