Modern and fossil traces in terrestrial lithic substrates

A number of biogenic processes leads to the formation of distinctive traces in terrestrial lithic substrates. These include: burrowing by vertebrates in moderately lithified rocks; scraping by mammals; smoothing and polishing of limestone surfaces by the locomotion of mammals; excavation by bees, wasps, and ants producing nesting and dwelling tunnels; dissolution of limestone surfaces by terrestrial snails; endolithic activity of fungi, algae, and lichens on subaerial rock surfaces; root corrosion; etc. Processes of biochemical weathering, biophysical erosion, and enlargement of cracks and fissures by the pressure of plant roots do not leave distinctive traces and therefore lie outside the ichnological realm. The fossil preservation of terrestrial bioerosional traces is expected to be uncommon. Nevertheless, various possible means of preservation must be considered, such as by rapid burial by volcanic material, by fluvial sediments, by travertine or tufa, by loess, “conservation”; in caves, case hardening of surfaces of porous rocks, and preservation of subsoil traces below fossil soils.