Response of macrobenthic trace maker community to the end-Permian mass extinction in Central Spitsbergen, Svalbard

Abstract

The End Permian Mass Extinction (EPME, ca. 252 Ma) is considered as the most severe biodiversity crisis in the Phanerozoic, affecting more than 90% of marine species and 75% of terrestrial species. In recent years, ichnological analysis has emerged as a proxy to better understand the paleoenvironmental changes associated with this event, as well as their effect(s) on the biota and its recovery. This study focuses on the ichnological analysis of an extended upper Permian – Lower Triassic succession from the DD-1 core, drilled in Deltadalen, Central Spitsbergen. Variations in degree of bioturbation and ichnodiversity across the Permian-Triassic transition allow for the characterization of pre-, syn-, and post-EPME phases. Pre-EPME is characterized by a high degree of bioturbation (BI = 5), and a diverse trace fossil assemblage (13 ichnotaxa) with abundant Nereites, frequent Planolites and Phycosiphon, and the more or less local record of Asterosoma, Bergaueria, Chondrites, Macaronichnus, Palaeophycus, Taenidium, Teichichnus, Thalassinoides, Zoophycos, meniscate horizontal burrows and undifferentiated vertical traces, indicative of oxygenated bottom and pore-waters, as well as high nutrient availability in the benthic habitat. The EPME was followed by an interval characterized by the scarcity (BI = 1) or even absence (BI = 0) of trace fossils. The decrease in ichnodiversity was abrupt at first and more progressive subsequently, as the conditions were inhospitable (i.e., very low oxygenation) in the benthic habitat. In this context, short-lasting episodes of improved paleoenvironmental conditions (from anoxia to dysoxia) allowed for intermittent colonization of the substrate. The post-EPME interval is characterized by a gradual recovery of the trace maker community in terms of abundance (BI from 1 to 5) and ichnodiversity (total of 10 ichnotaxa), revealing a relatively rapid reestablishment of favourable paleoenvironmental conditions for the benthic habitat, with better‑oxygenated bottom and pore-waters, as well as improved nutrient availability at or just below the seafloor. This new ichnological information highlights (i) the absence of a total extinction of the trace-maker community, despite a marked reduction in abundance and ichnodiversity during the EPME, and (ii) the rapid recovery of the benthic fauna during the Induan Age, ca. 150 kyr after the EPME occurred.