Abstract
At the boundary between the Paleozoic and Mesozoic eras (~ 252 myr), the end-Permian mass extinction was the most devastating global-scale event ever recorded, resulting in the loss of more than 90 % of marine species (Raup 1979) and the disappearance or severe reduction in diversity of typical Paleozoic organisms (e.g., trilobites, tabulate and rugose corals, brachiopods). The ecological recovery of the benthos is traditionally assumed to have spanned the entire Early Triassic (i.e. ~ 5 myr), thus strikingly contrasting with that of pelagic environments and their dwellers. Whether or not this difference is the result of a selective preservation bias against the benthos cannot be excluded. However, extreme diversity fluctuations of nekto-pelagic organisms (e.g., ammonoids and conodonts) during the entire Early Triassic indicate major environmental upheavals in the ocean in the wake of the end-Permian extinction(s). In support of markedly unstable Early Triassic times, several major events are known from the sedimentary, geochemical and palynological records (e.g., Payne et al. 2004, 2010; Galfetti et al. 2007a, b, c; Hermann et al. 2011, 2012; Sun et al. 2012; Grasby et al. 2013; Romano et al. 2013; Fig. 17.1a), suggesting profound global changes in climate, sea-level and oceanic geochemistry (e.g. anoxia, euxinia, acidification). The initial low resolution time frames of These recurrent environmental deterioration events after the Permian-Triassic boundary (PTB) crisis were therefore first lumped into a “delayed recovery” model which is still the standard in effect in some recent reviews (e.g., Chen and Benton 2012).
Brayard, Arnaud