Contrasting geochemical signatures on land from the Middle and Late Permian extinction events

Abstract

The end of the Palaeozoic is marked by two mass-extinction events during the Middle Permian (Capitanian) and the Late Permian (Changhsingian). Given similarities between the two events in geochemical signatures, such as large magnitude negative d 13 C anomalies, sedimentological signatures such as claystone breccias, and the approximate contemporaneous emplacement of large igneous provinces, many authors have sought a common causal mechanism. Here, a new high-resolution continental record of the Capitanian event from Portal Mountain, Antarctica, is compared with previously published Changhsingian records of geochemical signatures of weathering intensity and palaeoclimatic change. Geochemical means of discriminating sedimentary provenance (Ti/Al, U/Th and La/Ce ratios) all indicate a common provenance for the Portal Mountain sediments and associated palaeosols, so changes spanning the Capitanian extinction represent changes in weathering intensity rather than sediment source. Proxies for weathering intensity chemical index of alteration, ΔW and rare earth element accumulation all decline across the Capitanian extinction event at Portal Mountain, which is in contrast to the increased weathering recorded globally at the Late Permian extinction. Furthermore, palaeoclimatic proxies are consistent with unchanging or cooler climatic conditions throughout the Capitanian event, which contrasts with Changhsingian records that all indicate a significant syn-extinction and postextinction series of greenhouse warming events. Although both the Capitanian and Changhsingian event records indicate significant redox shifts, palaeosol geochemistry of the Changhsingian event indicates more reducing conditions, whereas the new Capitanian record of reduced trace metal abundances (Cr, Cu, Ni and Ce) indicates more oxidizing conditions. Taken together, the differences in weathering intensity, redox and the lack of evidence for significant climatic change in the new record suggest that the Capitanian mass extinction was not triggered by dyke injection of coal-beds, as in the Changhsingian extinction, and may instead have been triggered directly by the Emeishan large igneous province or by the interaction of Emeishan basalts with platform carbonates.

When and how did the terrestrial mid-Permian mass extinction occur? Evidence from the tetrapod record of the Karoo Basin, South Africa

“…The existence of a concurrent tetrapod extinction event in the non-marine Karoo Basin, situated thousands of kilometres from the Emeishan LIP, would also suggest an extinction mechanism with a global influence, such as atmospheric disruption through the release of volcanic gases and large-scale contact metamorphism of biogenic rocks [11,39,41,42]. New geochemical data from the GLB at geographically disparate localities is not consistent with global warming resulting from the large-scale release of methane or volcanic CO 2 [20] and stable or cooling conditions may in fact have prevailed [43]. Acidification, short-term cooling and volcanically induced darkness, possibly linked to the onset of Emeishan volcanism, appear to be the most probable causes of extinction for marine animals at the end of the Guadalupian [39] and this could have affected terrestrial ecosystems through reduced photosynthesis.…”

Integrated multi-stratigraphic study of the Coll de Terrers late Permian–Early Triassic continental succession from the Catalan Pyrenees (NE Iberian Peninsula): A geologic reference record for equatorial Pangaea

“…This climatic shift is possibly related to that of the upper portion of the Alcotas formation in the Iberian Basin (De la Horra et al, 2012) and also to the climatic shift documented in the early late Permian of northern Pangaea (Retallack et al, 2006;Roscher and Schneider, 2006;Słowakiewicz et al, 2009). This may imply that the lower/upper URU boundary could be correlated with the middle-late Capitanian (around the middle Permian extinction event) (Retallack et al, 2006;Sheldon et al, 2014;Day et al, 2015). Nevertheless, the lower/upper URU boundary possibly represents a paraconformity or sedimentary hiatus (i.e., long periods of exposition and development of levels with large nodules; Fig.…”

Radiometric Constraints on the Timing, Tempo, and Effects of Large Igneous Province Emplacement

“…Uncertainties for Emeishan dates were not reported at the level to permit comparison of different tracers used [Y]; taking that systematic uncertainty into account would increase the uncertainty on each of the LIP dates, potentially allowing for greater overlap with the extinction constraint of Day et al (2015). Some geochemical studies of end-Guadalupian sections from various sections globally indicate little climatic disturbance at the time (Sheldon et al, 2014) or a diagenetic, rather than environmentally controlled carbon isotope excursion (Jost et al, 2014), which complicates the simple hypothesis of the Emeishan LIP causing the end-Guadalupian extinction.…”