COLORFUL TRACES: RAPID IMAGE COLOR-INTENSITY ANALYSIS IN ICHNOLOGICAL AND ZOOGEOMORPHOLOGICAL RESEARCH

Images of biogenic traces, from microscopic to mega-scale, contain a wealth of information that can be enhanced and analyzed using digital processing methods. Image color-intensity (ICI) analysis is emerging as a rapid and effective means of visualization, identification, and quantification of specific components within a 256-shade grayscale (GS) spectrum (black = 0 through white = 255). Using ImageJ or similar freeware, a spectrum of graphic materials can be analyzed (e.g., satellite, aerial, field, laboratory, and archival materials). With consistent shading angle within an image, relative shadow darkness becomes a proxy for ichnite depth (hypichnial or epichnial grooves) or height (ridges). In addition to photographs of traces, ICI is readily applied to geophysical evidence (e.g., georadar images of large traces), with signal amplitude correlated to subsurface interfaces or lithological anomalies (e.g., heavy-mineral concentrations). The latter can be also assessed using magnetic susceptibility techniques, with darker horizons (e.g., enriched in magnetite) corelated with inverse GS peaks (black = 255). A wide spectrum of filters, threshold functions, and instant feature recognition options allow for accentuation of specific features and computation of key metrics (perimeter, area, etc.). We present examples from a range of environmental settings, in order of decreasing scale: ungulate game trails in coastal regions (southern Ukraine); Pleistocene cave-bear claw marks (western Ukraine); Miocene ungulate (Pecoripeda isp.) and felid (Bestiopeda isp.) footprints from the Vialov collection (western Ukraine), Eocene avian traces (Utah, USA), beaver gnaw marks (Kansas, USA) and bark stripping (Pennsylvania, USA); avian predation traces (Belichnus isp.), as well as gastropod (Oichnus isp.) and sponge (Entobia isp.) borings (Atlantic Coast, USA). Our approach demonstrates that ICI is a viable technique for enhancing or accentuating otherwise subtle or masked biogenic patterns, as well as for providing useful quantitative information for further statistical analyses.