High-precision geochronology confirms voluminous magmatism before, during, and after Earth's most severe extinction

Abstract

The end-Permian mass extinction was the most severe in the Phanerozoic, extinguishing more than 90% of marine and 75% of terrestrial species in a maximum of 61 ± 48 ky. Because of broad temporal coincidence between the biotic crisis and one of the most voluminous continental volcanic eruptions since the origin of animals, the Siberian Traps large igneous province (LIP), a causal connection has long been suggested. Magmatism is hypothesized to have caused rapid injection of massive amounts of greenhouse gases into the atmosphere, driving climate change and subsequent destabilization of the biosphere. Establishing a causal connection between magmatism and mass extinction is critically dependent on accurately and precisely knowing the relative timing of the two events and the flux of magma. New U/Pb dates on Siberian Traps LIP lava flows, sills, and explosively erupted rocks indicate that (i) about two-thirds of the total lava/pyroclastic volume was erupted over ~300 ky, before and concurrent with the end-Permian mass extinction; (ii) eruption of the balance of lavas continued for at least 500 ky after extinction cessation; and (iii) massive emplacement of sills into the shallow crust began concomitant with the mass extinction and continued for at least 500 ky into the early Triassic. This age model is consistent with Siberian Traps LIP magmatism as a trigger for the end-Permian mass extinction and suggests a role for magmatism in suppression of post-extinction biotic recovery.

Keywords: Biosphere; Biotic Crisis; Geochronology; Large Igneous Province; Magmatism; Mass Extinction; Siberian Traps; climate change; end-Permian; evolution.

Fig. 1. Generalized map of the current extent of Siberian Traps LIP rocks.

Overlain on the map are sample names and locations, which are keyed by color to rock type. Base map and outcrop extent modified from (9). Stratigraphic sections for the Noril’sk and Maymecha-Kotuy sections showing lava stratigraphy and sample location. Stratigraphy modified from (11).

Fig. 2. Single-grain and weighted mean ²⁰⁶Pb/²³⁸U dates for Siberian Traps LIP sills, lavas, and pyroclastic rocks.

The population of single-grain analyses from which the weighted mean date is calculated is shown for each dated sample. The height of each single-grain date is proportional to the 2σ analytical uncertainty on that point. The horizontal rectangle through each population represents the 2σ uncertainty on the weighted mean, which itself is represented by a thin horizontal line. Translucent single-grain analyses are not included in the weighted mean calculations. The horizontal gray rectangle and dashed red line running the length of the figure represent the mass extinction interval and calculated date of the paleontologically defined P-T boundary, respectively (4). Samples are color-keyed to match Fig. 1. Raw data can be found in table S2.

Fig. 3. Stratigraphy, geochronology, and magnetic polarity for Siberian Traps LIP rocks and the Permian-Triassic GSSP at Meishan, China.

Placement of the Permian-Triassic boundary on the lava stratigraphy is based on magnetic polarity, geochemistry, and geochronology. Polarity for the Noril’sk and Maymecha-Kotuy sections from (–32). Paleopolarity for the GSSP section from (33). The Permian-Triassic boundary shown is defined by the first appearance datum of the conodont Hindeodus parvus and is shown as the solid red line. Placement of the P-T boundary from (4).

Fig. 4. Timeline through the late Permian and early Triassic showing the record of Siberian Traps LIP magmatism, the end-Permian mass extinction interval, and the carbonate carbon isotopic record.

Age model for the mass extinction from (4). Carbon isotope data from (4, 49). Carbon isotope record is scaled to time using dates from (4) and is segmented into Intervals (1 to 5) based on the placement of bracketing ash bed dates and record topology. Shading used for the intrusive rock timeline indicates that magma flux per unit time is uncertain between dated samples.