Monday, 18 August, 2025/ Edition 72

The Permian-Triassic boundary at 252 Ma marked the worst mass extinction of the Phanerozoic Eon (the past 540 million years) in which nearly 90 percent of marine and terrestrial species were wiped out. The boundary also signifies a major shift in world geology in many respects including paleoclimate (superhot in the Triassic) and fossil fuels (richer in Permian rocks). The Siberian Trap volcanism is often considered as the trigger for the Permian-Triassic Mass Extinction (PTME) — the Great Dying. In this edition of Core Elements, we first look at Siberian Traps and then the Early Triassic super greenhouse climate.  

Rasoul Sorkhabi

Editor, Core Elements

Siberian Traps Revisited

Siberian Traps on the Putorana Plateau in Russia / Wikipedia Commons

A comprehensive study of the Siberian Traps has been published in the Annual Reviews of Earth and Planetary Sciences.

Location: The Siberian Traps is a large igneous province (LIP) in central Russia, east of the Ural Mountains, north of the Central Asian Mountains, and west of the Lena River.

LIPs represent intraplate magmatism with an aerial extent of greater than 100,000 square kilometers, a volume of greater than 1 million cubic kilometers, and a brief eruption interval of 1–5 million years.

Discovery: Aleksander Czekanowski, a Polish leader exiled to Siberia, conducted geological expeditions in 1873–1875 and documented basaltic rocks of central Siberia. He called them Siberian Traps (from the Swedish word trappa, meaning “stairs” — of lava).

Dimensions: Their areal extent is difficult to estimate because of burial under sediments in the West Siberian Basin and erosion of exposed rocks on the Central Siberian Plateau.

It is estimated that 7 to 15 million cubic kilometers of plutonic and volcanic rocks were generated, making the Siberian Traps the largest continental ILP during Phanerozoic times. 

Rocks: Near-surface exposures of Siberian Traps comprise about

• 40 percent lava

• 20 percent volcaniclastics

• 40 percent intrusions (sill and dikes)

Origin: Several mechanisms have been proposed for the generation of Siberian Traps including:

1. Mantle plume

2. Lithospheric delamination

3. Subduction-driven magmatism

4. Edge-driven convection of mantle at a passive continental margin

5. Meteorite impact

Of these, the authors prefer deep mantle plume as the main cause associated with lithospheric delamination.

Age: 251.9 Ma with an eruption period of less than one million years (252.3 to 251.3 Ma) in three phases:

1. Pyroclastic and effusive eruption

2. Main intrusive activity, and

3. Lava effusion and intrusion

Buried Siberian Traps: A study in Gondwana Research sheds light on Siberian Traps beneath the West Siberian Basin.

Study Methods: The researchers used cores from 31 boreholes for petrographic examination, geochemical analysis, and U-Pb geochronology. In addition, they used well logs and seismic images.

Results:

• Geochemical data indicate silicic volcanic rocks derived from the partial melting of mafic lower continental crust due to mantle plume heating.

• The volcanic rocks are buried under 2.5 to 3.5 kilometers of sediments.

• Silicic volcanic rocks possibly occupy 100,000 square kilometers within the West Siberian Basin.

• U-Pb zircon ages of nine silicic lava samples clustered at 252.1 to 251.3 Ma.

• Silicic volcanic rocks are genetically related to mafic Siberian Traps.

 Implications:

• Volcanism and (probably more important) metamorphism associated with the generation of LIPs such as the Siberian Traps can drastically alter global environmental conditions, especially via releasing carbon dioxide and methane causing atmospheric hothouse and destabilizing ocean chemistry.

• There are causal links between the Siberian Trap magmatism and the PTME.

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Prolonged Super Greenhouse in Early Triassic

Permian-Triassic boundary at Frazer Beach Member of the Moon Island Beach Formation, Sydney Basin, Australia / Wikipedia Commons

Here is an enigma: Geochronological data of Siberian Traps — the culprit for the PTME — show that the main magmatism lasted only 500,000 years, starting at 252.2 Ma. However, the super greenhouse climate in the Early Triassic lasted for about five million years.

Two studies have tackled this issue: One published in Geology and the second in Nature Communications. Let’s take a look.

Study #1. High Atmospheric Carbon Dioxide

Michael Joachimski and colleagues in Geology have reconstructed the atmospheric CO₂ from the Late Permian through the Middle Triassic.

Study Method:

The researchers utilized carbonate paleosol pCO₂ data from sections in northwest China (Xinjiang Province), north China (Henan and Shanxi Provinces), Russia (South Ural foreland basin), South Africa (Karoo basin), and the United Kingdom (Dorset).

Study Results:

• Atmospheric pCO₂ shows a 4-fold increase from 412–910 parts per million volume (ppmv) in Late Permian (Changhsingian) to 2181–2610 ppmv in Early Triassic (Griesbachian).

• Lower pCO₂ concentrations of 343–634 ppmv were reached in the Middle Triassic (Anisian).

• These results are consistent with low-latitude sea-surface paleo-temperatures measured from oxygen isotopes on conodont apatite which indicate a climate temperature increase of 7–10 °C from 25 °C in Late Permian (Changhsingian) to 37 °C in Early Triassic (Griesbachian) as reported by the same authors in GSA Bulletin 2010.

Study Implications: Joachimski et al. suggest that despite very warm climates during Early Triassic

• Silicate chemical weathering to reduce atmospheric carbon dioxide was not effective enough.

• Instead, formation of authigenic clay on the sea floor was intensified.

• Interestingly, cherts often found in Permian rock records disappear in Late Triassic record but reappear in Middle Triassic.

Study #2. Evidence from Vegetation

Zhen Xu and colleagues in Nature Communications offer a different perspective on why the Early Triassic super-greenhouse conditions persisted for five million years after the volcanic episode.

Study Method: These researchers built a global fossil database including microfossil and palynology data and reconstructed spatial-temporal maps of plant productivity changes from the Late Permian to the Middle Triassic.

Study Results:

• The data show that there was major loss of terrestrial vegetation at the PT mass extinction, especially in the tropics.

• In the aftermath of the PTME, plant recovery was very slow in Early Triassic, which meant low levels of organic carbon sequestration and prolonged super greenhouse atmosphere.

Go deeper: Read these two studies in Geology and Nature Communications.

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