Colorimetric characterisation of flatbed scanners for rock/sediment imaging

Colour is a physical property of rocks and sediments that has the potential to provide key insights into composition, and by extension the physical and chemical processes governing deposition. The rapid, non-destructive measurement of colour using spectrophotometers is an increasingly popular way of generating long datasets (i.e. >1000 data points) suitable for high-resolution palaeoclimate analysis. Digital image analysis of core photographs is another commonly applied method of extracting colour information, but the application of flatbed scanners for direct rock and sediment colour measurement has not received widespread attention. Here, a simple calibration methodology is presented that demonstrates how scanners can be colorimetrically characterised. The technique offers a quantitative approach to colour analysis that is superior to the subjective comparison of rocks/sediments to Munsell colour charts. Moreover, the accuracy of the method makes rock and sediment scanning a viable alternative to colour analysis using spectrophotometers. The technique is applied to Late Pleistocene sediment samples from the Canterbury Basin, New Zealand (IODP 317, Site U1352B) to emphasise the utility and precision of the method and the tight relationship between sediment colour and composition.