Digital image analysis of outcropping sediments: Comparison to photospectrometric data from Quaternary loess deposits at Şanoviţa (Romania) and Achenheim (France)

The possibility to use colour data, as extracted from two selected loess-paleosol sequences, is discussed here. Colour data are a fast and inexpensive method of proxy data generation. We compare the outcome from analysing outcrop images taken by digital cameras in the field and spectral colour data as determined under controlled laboratory conditions. By nature, differences can be expected due to variations in illumination, moisture, and sample preparation. Outcrop inclination may be an issue for photographs; correction for this is possible when marks can be used for rectification. In both cases the data extracted from the images match the visual impression of the photos well, and are useful for obtaining a more quantitative measure for field observations. Smoothness (as measured by autocorrelation) is high for an image from Achenheim/France, where an image with a width of ca. 1.1 m and a depth of 1.6 m was analysed. Data from a narrower image part from Şanoviţa/Romania are noisier. In both cases, a significant correlation between data extracted by digital image analysis and laboratory measurements could be established, suggesting that image analysis is a useful tool where outcrop- and light-conditions allow good photographs with similar illumination, especially where high resolution proxy data is required.