GEMAS: Novel continental-scale patterns revealed in the spatial distribution of Cr in European agricultural soil – A systematic method validation

Following the Ni-focused experimental investigation, it was clear that a critical advancement in digital image analysis of geochemical data sets required the validation of the procedures used with another element. Chromium was selected because its geochemical behaviour closely mirrors that of Ni in both lithological context and surface processes. Our current study, conducted with rigorous methodological precision, aims to assess a novel geospatial technique capable of capturing spatially variable continental-scale element distribution patterns. To reduce localised anomalies, we applied a moving average filter to the TIN-based interpolated Cr data set. The processed grid was then subjected to digital image analysis, which highlighted several continental-scale spatial orientations — NE-SW, E-W, and NW-SE — that closely resemble those found in the Ni study. Notably, prominent NE-SW and ENE-WSW linear Cr structures were identified, aligning with the known structural imprints of the Variscan and Alpine orogenic belts. Elevated Cr variable concentrations mainly occur in the Balkans and Alpine regions, consistent with exposures of mafic to ultramafic lithologies. A striking east-west trending Cr feature, with lower concentrations northwards, was also observed within the terminal zone of the last major glaciation, aligning with Cr-depleted glaciofluvial deposits. Chromium anomalies with a NW-SE trend also occur in regions such as Fennoscandia, Hellenic Republic, northern Italy, and the Pyrenees, aligning with those for Ni. Beyond confirming the efficacy of image analysis techniques in uncovering and describing new geochemical spatial patterns, this research also reinforces the approach by showing a pronounced continental-scale spatial correspondence between Cr and Ni distributions.