Severest crisis overlooked—Worst disruption of terrestrial environments postdates the Permian–Triassic mass extinction

Abstract

Generally Early Triassic floras are believed to be depauperate, suffering from protracted recovery following the Permian–Triassic extinction event. Here we present palynological data of an expanded East Greenland section documenting recovered floras in the basal Triassic (Griesbachian) and a subsequent fundamental floral turnover, postdating the Permian–Triassic boundary extinction by about 500 kyrs. This event is marked by a swap in dominating floral elements, changing from gymnosperm pollen-dominated associations in the Griesbachian to lycopsid spore-dominated assemblages in the Dienerian. This turnover coincides with an extreme δ13Corg negative shift revealing a severe environmental crisis, probably induced by volcanic outbursts of the Siberian Traps, accompanied by a climatic turnover, changing from cool and dry in the Griesbachian to hot and humid in the Dienerian. Estimates of sedimentation rates suggest that this environmental alteration took place within some 1000 years. Similar, coeval changes documented on the North Indian Margin (Pakistan) and the Bowen Basin (Australia) indicate the global extent of this crisis. Our results evidence the first profound disruption of the recovery of terrestrial environments about 500kyrs after the Permian–Triassic extinction event. It was followed by another crisis, about 1myrs later thus, the Early Triassic can be characterised as a time of successive environmental crises.

Marine Early Triassic Actinopterygii from Elko County (Nevada, USA): implications for the Smithian equatorial vertebrate eclipse

“…In the aftermath of this catastrophic event, the surviving and newly evolved clades went through a series of subsequent crises during the Early Triassic, which selectively affected their recovery (e.g., Galfetti et al, 2007b;Orchard, 2007;Brayard et al, 2009Brayard et al, , 2011Brayard et al, , 2017Song et al, 2011;Hofmann et al, 2013a, b;Hochuli et al, 2016).…”

“…These stages are well defined by global biotic events (e.g., Galfetti et al, 2007b;Hochuli et al, 2016). Recent biochronostratigraphic datings indicate a duration of maximally 1.4 ± 0.4 myr (million years) for the Griesbachian-Dienerian interval, 0.7 ± 0.6 myr for the Smithian, and~3 myr for the Spathian (Ovtcharova et al, 2006;Galfetti et al, 2007a).…”

New data from Oman indicate benthic high biomass productivity coupled with low taxonomic diversity in the aftermath of the Permian–Triassic Boundary mass extinction

“…Although not documenting the basal Griesbachian, this second record suggests that the Dienerian was significantly warmer than both Griesbachian and early Smithian times. The palynological record from NE Greenland also indicates that the main ecological crisis of terrestrial plants was not earlier than the Griesbachian-Dienerian boundary (Hochuli et al 2016). Moreover, a model initially proposed by Renne et al (1995) and recently revitalized by Baresel et al (2017) emphasizes a fast cooling at the PTB triggered by atmospheric injections of sulphur-rich volatiles from the Siberian Traps.…”

“…The palynological record from NE Greenland also indicates that the main ecological crisis of terrestrial plants was not earlier than the Griesbachian–Dienerian boundary (Hochuli et al . ). Moreover, a model initially proposed by Renne et al .…”

“…() concluded that a brief ice age (90 ± 38 kyr) that caused the global regression coinciding with the PTB was followed by a transient Griesbachian climate due to slower accumulation of CO 2 , until greenhouse conditions were reached not earlier than the Dienerian (Hochuli et al . ).…”