EARLY TRIASSIC OCEANIC ANOXIC EVENTS AND THE RECOVERY OF PELAGIC ECOSYSTEMS
The fate of the world’s pelagic fauna closely corresponds to the onset of the anoxia in the latest Permian when radiolarian productivity crashed and ammonoids were nearly annihilated. However, this link between the fate of pelagic groups and ocean redox changes is not seen again in the Triassic with the possible exception of the Smithian/Spathian anoxic event, when many ammonoids and conodonts were lost. Many pelagic groups diversified rapidly at some point in the Early Triassic (e.g. ammonoids in the Griesbachian, radiolarians in the latest Spathian and many fish groups throughout the interval). This non-coincidence is especially stark in the later Spathian Stage when anoxia intensified in both oceanic and shelf settings and yet fish and ammonoids were recovering rapidly at this time and radiolarian productivity and diversity was beginning to recover from an end-Permian “blackout phase”. Other factors, especially ocean temperature which is in clear lock-step with diversity, are probably much more important controls on pelagic radiations.