2005, Sören Jensen, Mary L. Droser, James G. Gehling, Trace fossil preservation and the early evolution of animals, Loren E. Babcock, Interpretation of Biological and Environmental Changes across the Neoproterozoic-Cambrian Boundary, Elsevier, page 26,
The distinction between a trace fossil and a pseudofossil is far from trivial (see discussion in Ekdale et al., 1984, pp. 29–36).
Source: wiktionary
Although these criteria seem precise, establishing the biogenicity of ancient fossils has proven to be the most difficult task. This is largely due to the facts that pseudofossils can mimic convincingly the characteristics of microfossils, and that an Archean microfossil record to which objects can be compared is very rare (Schopf and Walter, 1983; Schopf, 204).
Source: wiktionary