Being able to visualize three-dimensionally is essential when studying trace fossils. Except for their entrances, borings are often difficult to observe directly because they are situated in hard substrates such as bones, rocks, and shells. Multiple cross sections of the substrate may solve this problem. Yet, a more convenient method is casting, especially of microscopic borings. We suggest here an easy and fast way to cast. At room temperature the dried sample is embedded in Epofix (epoxy), using a vacuum chamber before hardening begins. Afterward the sample is removed chemically (e.g., by using a weak acid), leaving the cast.
The procedure was tested on shells from an infaunal bivalve, the ocean quahog (Arctica islandica Linné 1767) collected from Pleistocene deposits in northern Russia, and on recent shells of an epifaunal gastropod collected off Rhodes, Greece. Both types of shells contained micron-sized borings, which were successfully cast by the procedure.
Casts may give important knowledge on paleoecology and paleoenvironmental changes, such as the extent the tracemakers explored the substrate, and how many times colonization of the substrate occurred. Many tracemakers, e.g., fungi and algae, do not usually leave any body fossils. Without their borings and casts, it would be even more difficult to reconstruct biocoenoses.
Araldite: Araldites are glycerol-based aromatic epoxy resins.
Boring: Biogenic structure excavated into a hard substrate, e.g., rock, shell, or wood. The structure is made in a chemical and/or mechanical way ( Ekdale et al. 1984).
Epon 812: A glycerol-based aliphatic epoxy resin.
Epoxy: A thermosetting resin, having the property of becoming permanently hard and rigid when heated or cured. Syn.: epoxy resin, epoxy glue.
Resin: Any of a class of solid or semisolid viscous substances obtained either as exudations from certain plants or prepared by polymerization of simple molecules.
Trace fossil: Biologically-produced sedimentary structures that reflect behavioral patterns. Also included in trace fossils are borings in hard substrates and fossilized fecal material.
Vestopal: A polyester resin that is a copolymer between a polyester of maleic and fumaric acids, esterified with di- and tri- hydroxyalcohols and styrene.
Jan Kresten Nielsen. Geological
Museum, University of Copenhagen, Řster Voldgade 5-7, DK-1350 Copenhagen K,
Jesper Maiboe. Geological Institute, University of Copenhagen, Řster Voldgade 10, DK-1350 Copenhagen K, Denmark.