COMPLEX PATTERNS OF COMMUNITY RECOVERY FOLLOWING THE PERMIAN-TRIASSIC MASS EXTINCTION: PERCEPTION OF RECOVERY IS SCALE-DEPENDENT

The Permian-Triassic mass extinction was the largest extinction of the Phanerozoic, and is attributed to Siberian Traps volcanism and resulting climate change. Recent studies have shown that timing and mode of recovery from the extinction in the Early Triassic is highly complex, differing between regions, depositional environments, and community types. Some of this complexity has been attributed to ongoing environmental perturbations, stemming from repeated volcanic outgassing after the initial extinction event. The importance of specific localized environmental factors in the timing of recovery and community sensitivity to perturbations following the extinction is the topic of ongoing study. Here, two local-scale studies of changes in community complexity associated with geochemical proxies of carbon cycle perturbations are presented, one from a Panthalassic section, and one based on two Tethyan sections. Shallow-shelf benthic communities from the Panthalassic section show a trend of recovery relatively early in the Early Triassic, which subsequently fails in association with a large negative carbon isotope excursion. Due to a lack of sedimentological evidence for oxygenation and sedimentation changes, a spike in sea surface temperatures, associated with a recurrence of volcanic outgassing, is implicated as a shared causal mechanism between failed recovery and carbon cycle excursions. In comparison, the two Tethyan sections show no clear association of changes in community complexity and carbon isotope shifts, despite large positive and negative excursions occurring within the section. The shallower settings of these sections, in addition to frequent bathymetric and lithologic changes throughout, were likely overprinting observable community responses to larger global-scale mechanism of carbon cycle shifts, such as the response to thermal stress observed in the Panthalassic section. At the global scale, short term and localized patterns are lost, leading to a perception of the recovery of community complexity following the Permian-Triassic as a gradual process. Local-scale studies reveal repeated attempts in response to the impact of both global scale environmental perturbations, like reoccurring extreme temperature events, in conjunction with the effects of local processes.