Siberian Traps and the Permian-Triassic Mass Extinction
First Place
WRTG A213: Writing and the Sciences
Dr. Sheri Denison
Jack Foisy is finishing his third year at Mat-Su College, and his second year towards a bachelors in Geological Sciences. He is incredibly passionate about his chosen field and is looking towards graduate school in the future. He spends his time reading, hiking and pretending to write, and is actively looking for any opportunity to further his desired career of Geological research. He's hoping to make his way into the United States Geological Survey when he's finished with school. You can often find him pondering the universe or the vast geology of Alaska. He will drop everything if you show him a rock. Any rock.
Abstract
By examining articles of recent research into the Siberian Traps large igneous province and the Permian-Triassic mass extinction, this paper attempted to combine multiple works in order to analyze the possible connection between the two events. The research has provided substantial evidence of a connection, including the timing of the events, the expected results of volcanism in the Siberian province compared to those seen in the fossil record, and connections between the pulsed eruptions of the traps and the extinctions. This evidence has led to the conclusion that it is highly probable that the two events are connected. However, there are still gaps which must be accounted for and information which must be expanded upon and verified before this claim can be established.
Siberian Traps and the Permian-Triassic Mass Extinction
Approximately 250 million years ago, at the end of the geological period known as the Permian, a large series of volcanic eruptions across the entire Siberian sub-continent created a massive large igneous province[1] known as the Siberian Traps. This eruption is known as a flood basalt, where millions of cubic kilometers of basalt erupt across a large region in a geologically short period of time (Callegaro et al., 2021; Martinetto et al., 2020; Reichow et al., 2009). Occurring nearly congruously with this eruption was the Permian-Triassic mass extinction (PTME), the most cataclysmic mass extinction in the history of the Earth. During the extinction, nearly 90% of all animals on the planet were wiped out by numerous environmental changes. The time was fraught with catastrophic temperature increases, along with anoxia<[2] and acidification of the oceans (Baojin et al., 2021; Martinetto et al., 2020; Xulong et al., 2018). Whether or not these events were related is still subject to debate, since precise timing is difficult to accomplish due to the age of the events (Augland et al., 2019; Reichow et al., 2009). This literature review will examine research into these topics from the past five years and attempt to conclude the viability of the Siberian Traps-PTME theory. It will analyze when both events occurred and how long each lasted, what the fossil record says are the direct causes for the extinction (what directly lead to the deaths and extinction of plants and animals), what the eruption of the Siberian Traps would have caused based on geological data of the region, and an investigation into any alternate theories that may have caused the extinction.
1. Timing and Extent
The eruption of the Siberian Traps corresponds temporally to the PTME, but getting an exact date for these events can be difficult. In 2009, Reichow et al. used argon-argon radiometric dating to determine the age of some volcanic products among the Siberian Traps. Their analysis, which covered a large portion of the province, found a median age of about 250 million years old. However, these ages came with significant error, with some ages having more than 2.5 million years of error. This confirmed the approximate age of the eruption, but it did little to narrow the eruption to the precision needed for any sort of comparative analysis with the PTME. Further research provided by Augland et al. (2019) used lead-uranium dating to determine a mean weighted age of 251.46 ± 0.31 million years ago. The oldest specimen analyzed gave a mean result of 251.64 ± 0.11 million years ago. This value is significantly more accurate, providing a much more precise estimate on when volcanism in the Siberian Traps began.According to Martinetto et al. (2020), there are some inconsistencies in the date range for the PTME, with separate studies conducted in different regions showing different results. Nonetheless, it is widely believed that the extinction began at least 40,000 years before the Permian-Triassic boundary, which is set at 251.902 million years ago (Martinetto et al., 2020). That age would put the start of the extinction within a very short margin of time with the earliest rocks from the Siberian Traps eruption. However, this would suggest that the extinction began before extrusive[3] volcanic activity was present in Siberia. Burgess et al (2017) provide an answer however, as they suggest that the eruption occurred before magma reached the surface due to interactions between the magma and the carbonate[4] [5]. This theory does appear valid and is further strengthened by a paper by Elkins-Tanton et al. (2020), which shows that heated coal beds beneath Siberia may have accounted for this correlation. This could also account for why there is a disparity between the duration of the PTME and the Siberian Trap volcanism, with some estimates putting the initial pulse of the extinction to as short as 60,000 years, while the initial eruption of the Siberian Traps are estimated to have lasted up to 1 million years (Augland et al., 2019; Joachimski et al., 2020; Martinetto et al., 2020).
2. Direct Cause of Death
The PTME was responsible for the extinction of 96% of all marine species and nearly 50% of all extant marine families, along with 70% of terrestrial species. The rocks from the Permian-Triassic boundary provide significant suggestions as to the cause of these deaths. As noted by a number of studies, carbon records show that there was a significant temperature increase along the Permian-Triassic boundary, with temperatures rising by as much as 8°C worldwide and ocean temperatures rising by nearly 10°C (Joachimski et al., 2020; Jurikova et al., 2020; Martinetto et al., 2020; Yuyang et al., 2021). According to a study by Garcia-Soto (2021), an increase in ocean temperature tends to cause oxygen to dissolve more poorly in water, which can lead to anoxia throughout the ocean. This anoxia is found in the stratigraphic record[6] during this period in the form of oxygen poor minerals and oxygen isotopes in fossils, solidifying one of the more direct causes of death for marine animals (Baojin et al., 2021; Martinetto et al., 2020). In addition, there is evidence for oceanic acidification during this period (Jurikova et al., 2020; Martinetto et al., 2020). Acidification of the oceans can be very deadly to marine species, and some have suggested that it may have been one of the ultimate factors for the PTME (Jurikova et al., 2020). However, Joachimski et al. (2020) demonstrate that acidification was documented after the initial extinction pulse, and thus is unlikely to have contributed initially.For terrestrial environments, the intense heating would prove fatal to animals in the tropics. In fact, tropical fossils, both terrestrial and marine, showed a sharp decline during the PTME, providing evidence of either mass migration or extinction due to the intense temperatures (Bernardi et al., 2018). At the time the terrestrial environments were dominated by several groups of tetrapods, with reptiles, and therapsids, the precursors to all mammals, being the two most extant groups. Towards the end of the PTME, there was a significant decrease in tetrapod biodiversity, demonstrating that the majority of tetrapods did not survive the changing climate.
Research into plants during the PTME has been inconclusive, with contradictory results from several articles across the world. Daoliang et al. (2017) provided research into plants during this period, and noted that the Permian-Triassic boundary showed a significant reduction in coal, suggesting that the plants that would normally form coal were less prominent than before. On the contrary, Nowak et al. (2019) states that plant diversity did not experience a significant decrease during the PTME, and that evidence of such was an underrepresentation among global plant fossils. Their paper analyzed plant fossils, plant spore distribution and overall diversity of plant species during the Permian-Triassic boundary and concluded that plants did not experience a mass extinction at the time, with less than 19% of plant species experiencing extinction. The implications of this are still not fully understood, although they do state that the interactions between plants and animals likely influenced the extinction.
3. Siberian Traps Eruptions
The Siberian Traps represents one of the most massive large igneous provinces in the world, with volcanic products covering at least 1.5 million square kilometers (Callegaro et al., 2021; Martinetto et al., 2020). The eruptions from the traps were so vast that rocks found more than a thousand kilometers apart shared a similar geochemistry, suggesting an enormous magma system beneath the crust. The eruptions would have consisted of hundreds of volcanic vents pouring highly viscous magma across the continent, an eruption type often called Hawaiian due to the prominence of this type of eruption on the Hawaiian islands. (See Figure 1.)Figure 1
Approximate Known Scale and Location of the Siberian Traps Large
Igneous Province
Note: Approximate size and location. From “The Main Pulse of the Siberian Traps Expanded in Size and Composition,” by L. E. Augland, V. V. Ryabov, V. A. Vernikovsky, S. Planke, A. G. Polozov, S. Callegaro, D. A. Jerram, and H. H. Svensen, 2019, Scientific Reports, 9(18723). https://doi.org/10.1038/s41598-019-54023-2
While the direct cause for the eruption is disputed, there are a number of theories, such as a mantle plume[7] or delamination[8] of the crust. What we do know is that the multi-phase eruption lasted for about 5 million years (Martinetto et al., 2020). While a volcanic eruption of this magnitude is guaranteed to cause environmental changes, Elkins-Tanton et al. (2020) provide evidence for a widely held theory as to the unique nature of the Siberian Traps. Deep beneath the Siberian region lies a series of coal beds and hydrocarbon reservoirs, which Elkins-Tanton et al. (2020) suggested may have contributed to the gaseous products of the eruption. In their paper, they note that the fossil record demonstrates that an event known as a carbon isotope excursion occurred during the PTME. This carbon isotope excursion is also noted by a number of other studies (Augland et al., 2019; Baojin et al., 2021; Joachimski et al., 2020; Jurikova et al., 2020; Martinetto et al., 2020; Sibik et al., 2021; Yuyang et al., 2021). As explained by Vervoort et al. (2019), carbon isotope excursions are connected to large releases of carbon into the atmosphere. This carbon isotope excursion is examined further in a paper by Yuyang et al. (2021), wherein fossil carbon was analyzed to determine the atmospheric quantity of carbon molecules. They found that atmospheric carbon increased by nearly 6 times the value prior to the extinction, and the increase lined up with the carbon isotope excursion nearly perfectly. To explain this drastic increase in atmospheric carbon, Elkins-Tanton et al. (2020) concluded that the coal and oil beds beneath Siberia were heated and burned by the magma system growing beneath the surface, as the oldest rocks found within the traps are of similar age to the start of the carbon isotope excursion (Callegaro et al., 2021). The heating of these coals, gases, and oils would produce a significant amount of carbon dioxide and methane gas, both of which are strong greenhouse gases. Accompanied with the gases dissolved within the magma, the byproducts of this eruption would have released astronomical quantities of gases into the atmosphere. Further research by Sibik et al. (2021) adds that the chemical makeup of local sediments present among the Siberian Traps would have contributed to a significant release of gases, which had the potential to cause acid rain and further climate damage. The paper by Yuyang et al. (2021) suggests that as much as 12,000 gigatonnes of carbon dioxide alone were released into the atmosphere, although they state that with the current understanding of how carbon dioxide reacts in the atmosphere, even this may be an underestimate. This volume of CO2, which is nearly five times the quantity emitted by humans since the onset of industrialization, would lead to a runaway greenhouse effect, causing global temperatures to skyrocket.<
4. Discussion
In the past, several other theories have been suggested including a bolide (asteroid or comet) impact or degassing of oceanic methane. However, these theories were unable to account for every detail of the extinction event, and very few, if any, research papers released in the last 5 years advocate for any theory aside from Siberian Traps volcanism. Since this paper is only taking into account research done within the past half-decade and the fact that these theories lack significant evidence, they will not be examined further. On the other hand, assumptions should never be made in scientific research, so no theory should be ruled out without further research.With this in mind, we can see a potential correlation between the PTME and the Siberian Traps large igneous province. There is a significant amount of information suggesting that the Siberian Traps did indeed cause the PTME via a runaway greenhouse effect caused by volcanic gas emission and interaction with the local rocks. For example, the two events occurred within a very short geological time of each other, and although there is still some imprecision in the calculations, the proximity highly suggests a connection. Furthermore, the fossil record provides evidence for a large inpouring of carbon molecules into the atmosphere, something that would be expected from any volcanic eruption, but the scale of the increase suggests another variable (Burgess et al., 2017; Callegaro et al., 2021; Elkins-Tanton et al., 2020; Yuyang et al., 2021). That variable can be explained by the coal beds and hydrocarbon products beneath Siberia. These coal and gas beds would have been heated by the magma, causing it to burn, releasing billions of tons of carbon dioxide and methane into the atmosphere. This enormous release of greenhouse gases would cause an unparalleled environmental crisis, leading to staggering global warming and anoxia throughout the oceans. This climate disaster is exactly what is found among rocks and fossils from the Permian-Triassic boundary, with findings suggesting that temperatures rose by more than 10°C during the course of the extinction (Baojin et al., 2021; (Bernardi et al., 2018; Burgess et al., 2017; Callegaro et al., 2021; Daoliang et al., 2017; Elkins-Tanton et al., 2020; Joachimski et al., 2020; Jurikova et al., 2020; Martinetto et al., 2020; Xulong et al., 2018; Yuyang et al., 2021).
The topic of the PTME has been heavily studied for more than a century, yet there is still a considerable amount of unanswered questions. Did terrestrial plants actually suffer a mass extinction alongside animals? There seems to be a significant amount of doubt and incongruity among researchers, with some finding definitive evidence and others suggesting that plant extinctions were localized and that, globally, plants did not experience mass extinction (Daoliang et al., 2017; Nowak et al., 2019). Understanding how plants responded to the changing environment of the Permian-Triassic boundary would provide significant insight into the changes experienced by the terrestrial ecosystem. Furthermore, research into the Siberian Traps has been slowed due to the difficulty in collecting samples among the Siberian terrain (Callegaro et al., 2021). A significant amount of the rock strata from the period is buried under several kilometers of sediment and volcanic rocks. In some places, the basalt from the eruption reaches more than 4 kilometers in thickness (Callegaro et al., 2021; Reichow et al., 2009). Additionally, much of Siberia is taiga or cold steppe, with mountains, lakes and forests making travel difficult. This, combined with the depth of rock strata and remoteness of the samples, makes the collection of rock samples arduous, limiting the supply for future and current research. Further effort to collect samples from a wider range of areas could provide great insight into volcanism from the period. A topic of equally important study is the coal beds beneath Siberia, since study into their interactions with the magma system of the eruption is limited and fairly new. This is a topic that deserves more attention, given that gaining an understanding of the interactions between the magma and the hydrocarbons could be the key to understanding the entire extinction. Several other flood basalts have occurred congruously with mass extinctions, but no extinctions have been as severe as the PTME, providing more evidence that the Siberian Traps are unique among large igneous provinces. The hydrocarbons could be the cause of their uniqueness, and discerning that could be critical for understanding future eruptions.
5. Conclusion
While there is still a significant amount of research needed before any conclusion can be made, it seems highly probable that the Siberian Traps did indeed cause the Permian Triassic mass extinction. With few alternate theories, especially in recent years, and a large body of evidence correlating the two events, it is difficult to miss the connection. In light of this, research on these topics should certainly continue, since the PTME was the most disastrous extinction event of all time. If this theory is correct, and gas emissions from the Siberian Trap volcanism was the cause for this extinction, then gaining a better understanding of the events surrounding the extinction and the eruption can help humans adapt to their changing environment. We currently face a similar climate crisis, with carbon and methane emissions leading to a greenhouse effect that threatens the world ecologically. By understanding how the world and ecosystem are affected by this change, we can hope to adapt to, or perhaps even subdue, the mass extinction event that is already underway (Al-Ghussain, 2019; Choi et al., 2020; IPCC, 2021). Additionally, the Earth is covered in at least a dozen large igneous provinces like the Siberian Traps, suggesting that flood basalts, although rare, are still fairly common across large enough time spans. Thus, by gaining an understanding of one of the largest and potentially most disastrous, we can better understand and prepare for when–not if–the next large-scale eruption occurs. Only through knowledge can the human race survive across geological timespans.References
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