Extinction and recovery patterns of the vegetation across the Cretaceous–Palaeogene boundary — a tool for unravelling the causes of the end-Permian mass-extinction

Abstract

High-resolution palynofloral signatures through the Cretaceous-Palaeogene boundary succession show several features in common with the Permian-Triassic transition but there are also important differences. Southern Hemisphere CretaceousPalaeogene successions, to date studied at high resolution only in New Zealand, reveal a diverse palynoflora abruptly replaced by fungi-dominated assemblages that are in turn succeeded by low diversity suites dominated by fern spores, then gymnosperm-and angiosperm-dominated palynofloras of equivalent diversity to those of the Late Cretaceous. This palynofloral signature is interpreted to represent instantaneous (days to months) destruction of diverse forest communities associated with the Chicxulub impact event. The pattern of palynofloral change suggests wholesale collapse of vascular plant communities and short-term proliferation of saprotrophs followed by relatively rapid successional recovery of pteridophyte and seed-plant communities. The Permian-Triassic transition records global devastation of gymnosperm-dominated forests in a short zone synchronous with one or more peaks of the fungal/algal palynomorph Reduviasporonites. This zone is typically succeeded by assemblages rich in lycophyte spores and/or acritarchs. Higher in the succession, these assemblages give way to diverse palynofloras dominated by new groups of gymnosperms. Although different plant families were involved in the mass-extinctions, the general pattern of extinction and recovery is consistent between both events. The major difference is the longer duration for each phase of the Triassic recovery vegetation compared to that of the Paleocene. The protracted extinction-recovery succession at the Permian-Triassic boundary is incompatible with an instantaneous causal mechanism such as an impact of a celestial body but is consistent with hypotheses invoking extended environmental perturbations through flood-basalt volcanism and release of methane from continental shelf sediments.

The Triassic to Early Jurassic palynological record of the Tarim Basin, China

“…The vegetation reconstruction for the Triassic of the Tarim Basin shows that, based on palynology, the effects of two mass extinction events are reflected in the vegetation composition. The Early Triassic assemblages in the TT1 zone are characterised by abundant bryophytes and Densoisporites spp.-producers, a well-known marker for the Early Triassic recovery succession following the end-Permian event (Vajda and McLoughlin 2007). Two spore peaks recorded in the Upper Triassic and Lower Jurassic potentially reflect vegetation responses to the T-J extinction.…”

“…These Olenekian wetland communities are possibly a response of an allogenic succession of early pioneers represented by bryophytes and lycophytes that produced spores such as Limatulasporites limatulus and Densoisporites spp. This spore-producing vegetation was thriving globally following the end-Permian mass extinction, forming a marker for the recovery successions in continental environments (Looy et al 1999;Grauvogel-Stamm and Ash 2005;Vajda and McLoughlin 2007;Bercovici et al 2015).…”

Kerogen morphology and geochemistry at the Permian–Triassic transition in the Meishan section, South China: Implication for paleoenvironmental variation

“…The Bed 26 to Bed 27 were thought to be deposited in 10 4 to 10 5 years after the mass extinction on the basis of age dating by Bowring et al (1999). Thus, it seems that the timing of the high abundance of herbaceous organic matter in upper layer of Bed 26 was slightly later than that increasing pioneer herbaceous plant such as lycopsid and fern as suggested by Vajda and McLoughlin (2007). At that time, transport efficiency of terrigenous materials abundantly containing herbaceous plant possibly increased with a short duration.…”

“…This result suggests that herbaceous plants were remarkably dominant as pioneer plants in terrestrial ecosystem during early stage of recovery. Vajda and McLoughlin (2007) reviewed the recovery pattern of terrestrial vegetation during the PTB, and summarized that only fungal/algal palynomorph proliferated as disaster biota just after the mass extinction and damage of terrestrial ecosystem, then the opportunistic herbaceous lycopsids and fern increased, and subsequently pleuromeiid lycopsids, peltasperms and voltzialean conifers were abundant, and at last a diverse gymnosperm-rich floras were gradually returned. They estimated the timing of appearance of pioneer herbaceous plants to be less than 2-5 x10 4 years after the mass extinction.…”

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“…The findings include a relatively long time needed for recovery of vegetation (Eshet et al, 1995;Looy et al, 1999;Grauvogel-Stamm and Ash, 2005) and accumulation of large volume of decomposable organic matters and fungal spores, which indicate post-extinction circumstances (Steiner et al, 2003;Vajda and McLoughlin, 2007) as well as bisaccate pollens such as Falcisporites sp. & Alisporites sp.…”