EARLY TRIASSIC RECOVERY - A FALSE DAWN? (Invited Presentation)

The nature of the recovery from the Permo-Triassic mass extinction is currently the subject of intense debates that principally focus on the nature of the global environments: were conditions in the Early Triassic sufficiently “back-to-normal” that marine life was able to diversify unhindered or did they remain exceedingly harsh? In favor of the former alternative have been the recent discoveries of earliest Triassic metazoan reefs and locally high diversity benthic communities, whilst proponents of the latter point to the unusual attributes of the Early Triassic: low alpha diversity, small (Lilliput) taxa, a coal gap, and a biogenic chert gap. In addition, proxies for ocean temperature and marine redox indicate extraordinarily warm conditions and the frequent, widespread occurrence of intense anoxia, even in very shallow-water settings. Both these factors are likely to have impacted the recovery in the aftermath of extinction. The occurrences of an extinction within the Early Triassic, around the Smithian-Spathian boundary, further suggests inimical conditions may have intensified to the point that even the hardy survivors of the great mass extinction could not survive. In overview, the Early Triassic interval represents a time of harsh conditions and the longest aftermath/delayed recovery interval seen for any mass extinction crisis. Local evidence for recovery is typically associated with temporarily improved conditions, often in shallow water settings that allowed some degree of diversity increase, but they were false dawns, it was not until the Middle Triassic that true, prolonged recovery began.