ICHNOLOGY AND OUR UNDERSTANDING OF THE RECOVERY OF THE MARINE BENTHOS AFTER THE LATE PERMIAN EXTINCTION EVENT

Ichnology has a central role to play in our understanding of the recovery of the marine benthic ecosystem in the aftermath of extinction events large and small. Trace fossils have long been used to help infer paleoenvironmental change (e.g. identifying oceanic anoxic events). During extinction-recovery intervals, however, they also provide unique data concerning paleoecology and biotic change. Trace fossils are the only records of the responses of the majority (soft-bodied) marine benthos to mass extinction events. They provide evidence of changes in infaunal tiering, body size, the presence/absence of certain taxa of marine invertebrate, and possibly levels of primary productivity (although this is more equivocal). Patterns of change can be compared between extinction events and between regions after the same event. In the immediate aftermath of the Late Permian event the temporary disappearance of ichnotaxa inferred to have been constructed by infaunal suspension feeders may indicate a reduction in levels of primary production. Infaunal tiering was severely reduced by this event and the body sizes of tracemakers dramatically declined. The reappearance of ichnotaxa such as Arenicolites and Diplocreterion may correspond to the re-establishment of significant primary production, and mark the first increase in infaunal tiering in the extinction aftermath. Ichnotaxa attributed to crustaceans (e.g. Thalassinoides) take the longest to reappear, and in the aftermath of the Late Permian event normal-sized Thalassinoides apparently indicate final recovery of the benthic ecosystem. Globally, certain ichnotaxa reappear quicker in some regions than in others, reflecting variation in the rates of regional recovery in the aftermath of the Late Permian event. The benthic ecosystems in mid-high paleolatitude shelf seas apparently recovered quicker than those in the paleotropics.