Calibration of Short-Wave InfraRed (SWIR) hyperspectral imaging using Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFTS) to obtain continuous logging of mineral abundances along sediment cores

Abstract

Sediment cores are a major source of sub-surface data for a variety of environmental research endeavors, as well as mining and civil engineering applications. In paleo-environmental studies, fluctuations in mineral abundances along sediment cores are used to study climate change, sea-level variations, sediment dynamics, and landscape evolution. Increasing reliance on such proxies spurs the need for reliable and time-saving analytical tools and procedures. Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFTS) is a rapid, non-destructive and accurate tool for quantification of mineral abundances. We use DRIFTS to calibrate Short-Wave InfraRed (SWIR) hyperspectral images (HSIs) of a sediment core, in order to convert point-specific DRIFTS measurement of mineral abundances into a continuous record of mineral abundances along the core. Initially, single-phase and mineral assemblages of quartz, calcite, and clay mineral are created and measured by DRIFTS to establish calibration curves to convert DRIFTS data into mineral abundances, as %wt of bulk sediment samples. Mineral abundances are then measured by DRIFTS in a set of 60 samples from a core drilled into the Albegna River delta, Tuscany, Italy in the Fall of 2020. SWIR-HSIs of the core are then obtained and averaged over the areas corresponding to the samples taken for point-specific DRIFTS measurements. Least squares regressions are established between SWIR-HSI and DRIFTS data over these areas. This calibration is then used to convert SWIR-HSIs of the entire core into a continuous prediction of quartz, calcite, and clay mineral abundances along the core. The continuous record highlights sharp changes in mineral composition, smeared out in the discontinuous DRIFTS record. The advantages and limitations of the method, as well as its applicability to other sedimentary environments are discussed.