Application of portable VNIR and MIR spectroscopy for the analysis of physicochemical sediment characteristics and stratigraphy in drill cores of Holocene overbank deposits in Central Europe

Quaternary sediment successions provide valuable insights into Earth's recent geological history, contributing to our understanding of environmental change and climate dynamics. Detailed and reliable stratigraphies of Quaternary sediment outcrops or drill cores, however, often require time-consuming and expensive laboratory analyses. Diffuse reflectance spectroscopy in the visible-to-near-infrared (VNIR) and mid-infrared (MIR) ranges offers a fast and cost-effective alternative to obtain quantitative data on the mineral and organic composition of sediments. We therefore examined the potential of using portable VNIR and MIR spectroscopy on intact drill cores to assist in stratigraphic analysis, in particular how recently introduced handheld MIR instruments can improve the accuracy of spectroscopic modelling. Diffuse reflectance spectra were collected on two drill cores from Central European Holocene overbank deposits, which were subject to a comprehensive stratigraphic description and detailed conventional sedimentological and geochemical analyses. PLSR and PLS-DA were employed to evaluate the potential of spectroscopic models to estimate physicochemical sediment properties and to classify sediment layers and (paleo)soils, respectively. Geochemical sediment properties could be estimated with good accuracy (R2 = 0.74–0.96) reproducing major trends and features in the analysed cores. Classification results with coupled VNIR-MIR data were also promising (OA = 88.4 %), giving better accuracy than classification with conventional geochemical data (OA = 83.7 %), although the detection of weakly-developed paleosols proved challenging. Our results demonstrate that coupled VNIR-MIR spectroscopy with portable instruments can provide high-quality data on the geochemical composition of sediments and that handheld MIR spectroscopy can mark a major step forward in the analysis of Quaternary sediment profiles. As VNIR-MIR data collection is feasible directly on drill cores without a time-consuming pre-processing of samples, we suggest that portable VNIR-MIR spectroscopy can effectively complement conventional methods of sediment analysis and contribute to the establishment of reliable stratigraphies through the generation of large amounts of inexpensive quantitative sediment data.