RESEARCH

RESEARCH

Thomas J. Algeo

Professor of Geology

University of Cincinnati

Biocrisis at the Permian/Triassic Boundary: Causes and Consequences

The mass extinction at the Permian/Triassic boundary (PTB) was the largest biocrisis in Earth history, eliminating ~90% of marine species and ~70% of terrestrial species (right; Sepkoski, 2002). Eruption of the Siberian Traps flood basalts is regarded as the most likely cause of this crisis (Renne et al., 1995; Korte and Kozur, 2010), but the manner in which volcanic outpourings devastated the environment and biosphere is uncertain. I am investigating changes in environmental conditions in marine PTB sections having a global distribution, with the goal of better understanding the causes and consequences of this biocrisis.
The PTB mass extinction resulted in major changes in marine ecosystems. At Meishan (upper right), benthic marine faunas were sharply reduced in diversity, abundance, and range of ecological tiering from the Late Permian to the Early Triassic (Benton and Twitchett, 2003). The extinction event was broad, affecting many clades including calcareous algae, foraminifera, radiolarians, and others (lower right). Patterns of post-crisis recovery vary widely: some clades quickly exceeded their pre-crisis diversity levels (e.g., ammonoids), others were permanently reduced (e.g., brachiopods), while yet others went extinct in the aftermath of the crisis (e.g., bellerophontid gastropods). During the Early Triassic, some clades (e.g., bivalves and gastropods) exhibited a pronounced reduction in average size, termed the "Lilliput effect" (Twitchett, 2007). These ecosystem changes were accompanied by large fluctuations in marine carbonate d¹³C values (right; Payne et al., 2004), indicating major perturbations to the global carbon cycle for several million years during the Early Triassic. The summary figure at lower right is from Algeo et al. (2011a).	Late Permian Early Triassic

Despite decades-long study of the Permian- Triassic boundary, there are relatively few integrated, high-resolution chemostratigraphic datasets for marine sections that can address critical questions related to, e.g., the extent, intensity, and timing of deep-ocean anoxia, patterns of oxygen-minimum zone (OMZ) expansion and/or upwelling of toxic deep- ocean waters onto shallow-marine shelves and platforms, marine-terrestrial teleconnections, and the relationships of these events to the delayed recovery of Early Triassic marine biotas. My research program has generated integrated chemostratigraphic datasets for marine sections around the world in order to address these questions (map at right with sections numbered; adapted from Algeo et al., 2012a).
Earlier studies inferred that almost the entire global ocean went anoxic during the PTB crisis (Wignall and Twitchett, 1996, 2002), and that deep-ocean anoxia commenced as early as the early Late Permian, ~8 million years before the PTB mass extinction (Isozaki, 1997). These inferences are not in accord with the results of my recent studies. First, deep-sea sections from Japan show evidence of only limited changes in redox conditions on the deep seafloor (i.e., <2X increases in the concentrations of redox- sensitive elements in the Early Triassic black shale facies relative to the Late Permian gray chert facies; upper right, Algeo et al., 2010 and 2011b). In contrast, there is a huge (>6X) increase in the burial flux of S related to the appearance of pyrite framboids in the black shale facies (lower right). I inferred that the framboids were forming high in the water column, for example within the OMZ, rather than close to or below the seafloor. This inference is in accord with paleoceanographic models for the PTB (Kiehl and Shields, 2005; Winguth and Maier-Reimer, 2005; Winguth and Winguth, 2012).
Second, the timing of changes in ocean redox conditions during the Late Permian-Early Traissic has been extensively debated. While small changes may have occurred in advance of the PTB crisis, U isotope analysis of the Dawen (China) section demonstrates that a major shift toward more reducing conditions occurred at the level of the mass extinction horizon (Brennecka et al., 2011). This study showed that d²³⁸U shifted rapidly from ca. -0.40‰ to ca. -0.65‰ (upper right). Mass balance calculations indicate that this shift is consistent with expansion of the anoxic sink for U by a factor of ~6X (from 10% to 60%; lower right). A synchronous shift in Th/U ratios from ~0.1 to ~0.6 is also consistent with a ~6X drawdown of U in seawater (upper right). These results demonstrate that the most important changes in ocean redox conditions were concurrent with the mass extinction event.
These findings suggest a major expansion of the oceanic oxygen-minimum zone (OMZ) during the PTB crisis. Expansion of the OMZ during the latest Permian is supported by recent analyses of radiolarian faunas in deepwater sections of the Nanpanjiang Basin (South China). At Dongpan, all families of radiolaria exhibit steep declines in diversity and abundance about 2 meters below the PTB mass extinction horizon (upper right; Shen et al., 2012a). This pattern indicates that deepwater biota were affected by an expanding OMZ about 100kyr prior to the main extinction event (lower right). That radiolarian were affected by a rising chemocline rather than by stresses imposed from the ocean surface is demonstrated by the observation that the albaillellarian family, representing the deepest dwelling radiolarians, went completely extinct at this time, whereas the relatively shallower-dwelling families (Latentifistularia, Spumelaria, and Entactinaria) declined but did not disappear (upper right).

Expansion of the oceanic OMZ during the Late Permian is implied also by biotic changes in the Sverdrup Basin of Arctic Canada. Sections in this region such as West Blind Fiord exhibit an abrupt extinction of siliceous sponges (the main biota of the Late Permian Sverdrup Basin), termed the "Arctic extinction event" (AEE) (Algeo et al., 2012b). Through detailed conodont correlations, my colleague, Charles Henderson of the University of Calgary, was able to show that the AEE is older than the latest Permian mass extinction (LPME) horizon in Tethyan PTB sections (Yin et al., 2012). The implication of this finding is that marine environmental stresses were felt earlier at high northern paleolatitudes than in the equatorial latitudes of the Tethys Ocean, possibly because of large-scale volcanic ash deposition or moderate pre-crisis climatic warming that disproportionately affected high-latitude regions (Algeo et al., 2011a).
These insights regarding expansion of the oceanic OMZ during the latest Permian help to make sense of biotic and geochemical changes at the LPME in shallow-marine sections. PTB sections such as that at Nhi Tao (Vietnam) accumulated on the top of a carbonate platform in the Nanpanjiang Basin at water depths of a few meters to tens of meters (right; Algeo et al., 2007a, 2008). Such sections commonly show an abrupt extinction horizon that coincided with (1) a ca. 3‰ negative excursion in carbonate d¹³C, (2) appearance of framboidal pyrite (S spikes) that is ³⁴S-depleted, and (3) near- complete loss of TOC (cf. Algeo et al., 2012a). This pattern is consistent with episodic upward movement of sulfidic deepwaters, possibly via the chemocline upward excursion mechanism of Kump et al. (2005), with the first such event resulting in decimation of benthic biotas and near-sterilization of shallow-marine habitats.
Another facet of my PTB research focuses on terrestrial-marine "teleconnections", i.e., fluxes of material between terrestrial and marine systems that might have played a role in marine environmental changes during the PTB crisis. An analysis of sediment fluxes revealed a nearly global increase in sediment accumulation rates during the earliest Triassic (right; Algeo and Twitchett, 2010). This increase is observed in both carbonate and siliciclastic facies in shallow-marine areas, owing to a higher flux of dissolved and particulate weathering products from continents, but not in deep-ocean areas that were far from continents and below the paleo-CCD (carbonate compensation depth). Increased continental weathering rates were probably due to a combination of higher surface temperatures, acid rainfall, and generally disturbed terrestrial landscapes (cf. Looy et al., 1999, 2001).
The findings above allow development of a revised model of relationships between the Siberian Traps flood basalt eruptions and the terrestrial and marine environmental-biotic crises (upper right, Algeo et al., 2011a; see Wignall, 2001, for original version of flowchart). Massive eruptions triggered strong warming through release of volcanic CO₂ and possibly also thermogenic methane following magmatic intrusions into the West Siberian Coal Basin (lower right). A combination of higher surface temperatures, acid rainfall, and generally disturbed terrestrial landscapes led to an increased flux of weathered material to shallow-marine areas. This flux included excess nutrients that locally stimulate marine productivity, which, in combination with warming-induced water-column stratification, resulted in a rapid expansion of the oceanic OMZ during the latest Permian. These conditions persisted, or recurred episodically for ~2 million years during the Early Triassic, resulting in a delayed recovery of terrestrial and marine ecosystems.

Work now in progress will address additional important issues related to the Permian-Triassic boundary crisis, including: seawater temperature changes associated with the crisis interval secular changes in seawater DIC C-isotope gradients, and their significance for water column stratification secular changes in seawater sulfate S-isotopes, and their significance for organic burial fluxes secular changes in continental weathering rates and nutrient fluxes to coastal marine systems the relationship of marine environmental changes to eruption of the Siberian Traps

References

Algeo, T., and Twitchett, R., 2010. Anomalous Early Triassic sediment fluxes due to due to elevated weathering rates and their biological consequences. Geology, v. 38, p. 1023-1026. doi: 10.1130/G31203.1.

Algeo, T.J., Chen, Z.Q., Fraiser, M.L., Twitchett, R.J., 2011a. Terrestrial-marine teleconnections in the collapse and rebuilding of Early Triassic marine ecosystems. Palaeogeography Palaeoclimatology Palaeoecology, v. 308, p. 1-11. doi:10.1016/j.palaeo.2011.01.011.

Algeo, T.J., Ellwood, B.B., Nguyen, T.K.T., Rowe, H., and Maynard, J.B., 2007a, The Permian-Triassic boundary at Nhi Tao, Vietnam: Evidence for recurrent influx of sulfidic watermasses to a shallow-marine carbonate platform: Palaeogeography Palaeoclimatology Palaeoecology, v. 252, p. 304-327, doi:10.1016/j.palaeo.2006.11.055.

Algeo, T.J., Hannigan, R., Rowe, H., Brookfield, M., Baud, A., Krystyn, L., and Ellwood, B.B., 2007b. Sequencing events across the Permian-Triassic boundary, Guryul Ravine (Kashmir, India): Palaeogeography Palaeoclimatology Palaeoecology, v. 252, p. 328-346, doi:10.1016/j.palaeo.2006.11.050.

Algeo, T., Henderson, C., Ellwood, B., Rowe, H., Elswick, E., Bates, S., Lyons, T., Hower, J.C., Smith, C., Maynard, J.B., Hays, L., Summons, R., Fulton, J., Freeman, K., 2012b. Evidence for a diachronous Late Permian marine crisis from the Canadian Arctic region. Geological Society of America Bulletin, v. 124 (9/10), p. 1424-1448. doi:10.1130/B30505.1.

Algeo, T.J., Henderson, C.M., Tong, J., Feng, Q., Yin, H., Tyson, R., 2012a. Plankton and productivity during the Permian-Triassic boundary crisis: An analysis of organic carbon fluxes. Global and Planetary Change, in press. doi:10.1016/j.gloplacha.2012.02.008.

Algeo, T.J., Hinnov, L., Moser, J., Maynard, J.B., Elswick, E., Kuwahara, K., and Sano, H., 2010. Changes in productivity and redox conditions in the Panthalassic Ocean during the latest Permian. Geology, v. 38, p. 187-190. doi:10.1130/G30483.1.

Algeo, T.J., Kuwahara, K., Sano, H., Bates, S., Lyons, T., Elswick, E., Hinnov, L., Ellwood, B.B., Moser, J., and Maynard, J.B., 2011b. Spatial variation in sediment fluxes, redox conditions, and productivity in the Permian-Triassic Panthalassic Ocean . Palaeogeography Palaeoclimatology Palaeoecology, v. 308, p. 65-83. doi:10.1016/j.palaeo.2010.07.007.

Algeo, T.J., Shen, Y., Zhang, T., Lyons, T.W., Bates, S.M., Rowe, H., and Nguyen, T.K.T., 2008, Association of ³⁴S-depleted pyrite layers with negative carbonate δ¹³C excursions at the Permian/Triassic boundary: Evidence for upwelling of sulfidic deep-ocean watermasses. Geochemistry Geophysics Geosystems, v. 9, Q04025, 10 pp., doi:10.1029/2007GC001823.

Benton, M.J., Twitchett, R.J., 2003. How to kill (almost) all life: the end-Permian extinction event. Trends in Ecology and Evolution 18, 358-365.

Brennecka, G.A., Herrmann, A.D., Algeo, T.J., Anbar, A.D., 2011. Rapid expansion of oceanic anoxia immediately before the end-Permian mass extinction. Proceedings of the National Academy of Sciences (USA), v. 108, p. 17631-17634, doi/10.1073/pnas.1106039108.

Isozaki, Y., 1997, Permo-Triassic boundary superanoxia and stratified superocean; records from lost deep sea: Science, v. 276, p. 235-238.

Kiehl, J.T., and Shields, C.A. , 2005. Climate simulation of the latest Permian: Implications for mass extinction. Geology v. 33, p. 757-760.

Korte, C., Kozur, H.W., 2010. Carbon-isotope stratigraphy across the Permian-Triassic boundary: A review. J. Asian Earth Sci. 39, 215-235.

Kump, L.R., Pavlov, A., Arthur, M.A., 2005, Massive release of hydrogen sulfide to the surface ocean and atmosphere during intervals of oceanic anoxia: Geology, v. 33, p. 397-400.

Looy, C.V., Brugman, W.A., Dilcher, D.L., Visscher, H., 1999, The delayed resurgence of equatorial forests after the Permian-Triassic ecological crisis: Proceedings of the National Academy of Sciences, v. 96, p. 13,857–13,862.

Looy, C.V., Twitchett, R.J., Dilcher, D.L., van Kojnijnenberg-van Cittert, J.H.A., Visscher, H., 2001, Life in the end-Permian dead zone: Proceedings of the National Academy of Sciences, v. 98, p. 7879–7883.

Luo, G., Wang, Y., Kump, L.R., Bai, X., Algeo, T.J., Yang, H., Xie, S., 2011b. Nitrogen fixation prevailed simultaneously with the end-Permian marine mass extinction and its implications. Geology, v. 39, p. 647-650. doi:10.1130/G32024.1.

Luo, G., Wang, Y., Yang, H., Algeo, T.J., Kump, L.R., Huang, J., and Xie, S., 2011a. Stepwise and large-magnitude negative shift in δ¹³C_carb preceded the main marine mass extinction of the Permian-Triassic crisis interval. Palaeogeography Palaeoclimatology Palaeoecology, v. 299, p. 70-82. doi:10.1016/j.palaeo.2010.10.035.

Payne, J.L., Lehrmann, D.J., Wei, J., Orchard, M.J., Schrag, D.P., Knoll, A.H., 2004. Large perturbations of the carbon cycle during recovery from the end-Permian extinction. Science 305, 506-509.

Renne, P.R., Zheng, Z.C., Richards, M.A., Black, M.T., Basu, A.R., 1995. Synchrony and causal relations between Permian–Triassic boundary crisis and Siberian flood volcanism. Science 269, 1413-1416.

Schoepfer, S.D., Henderson, C.M., Garrison, G.H., Ward, P.D., Foriel, J., Selby, D., Shen, Y., Hower, J.C., Algeo, T.J., 2012. Termination of a continent-margin upwelling system at the Permian-Triassic boundary (Opal Creek, Alberta, Canada). Global and Planetary Change, in press, doi:10.1016/j.gloplacha.2012.07.005.

Sepkoski, J.J., Jr., 2002. A compendium of fossil marine animal genera. Bull. Am. Paleontol. 363, 563 pp.

Shen, J., Algeo, T.J., Hu, Q., Xu, G., Zhou, L., Feng, Q., 2012b. Volcanism in South China during the Late Permian and its relationship to marine ecosystem and environmental changes. Global and Planetary Change, in press. doi:10.1016/j.gloplacha.2012.02.011.

Shen, J., Algeo, T.J., Hu, Q., Zhang, N., Zhou, L., Xia, W., Feng, Q., 2012c. Negative C-isotope excursions at the Permian-Triassic boundary linked to volcanism. Geology, in press (will appear in Nov. 2012 issue).

Shen, J., Algeo, T.J., Zhou, L., Feng, Q., Yu, J., Ellwood, B.B., 2012a. Volcanic perturbations of the marine environment in South China preceding the latest Permian extinction event and their biotic effects. Geobiology, v. 10, p. 82-103. doi: 10.1111/j.1472-4669.2011.00306.x.

Twitchett, R.J., 2007. The Lilliput effect in the aftermath of the end-Permian extinction event. Palaeogeogr. Palaeoclimatol. Palaeoecol. 252, 132-144.

Wignall, P.B., 2001. Large igneous provinces and mass extinctions. Earth-Sci. Rev. 53, 1-33.

Wignall, P.B., Twitchett, R.J., 1996. Oceanic anoxia and the end Permian mass extinction. Science 272, 1155-1158.

Wignall, P.B., Twitchett, R.J., 2002. Extent, duration, and nature of the Permian-Triassic superanoxic event. In: Koeberl, C., and MacLeod, K.G., eds., Catastrophic events and mass extinctions: Impacts and beyond: Geological Society of America Special Paper 356, p. 395-413.

Winguth, A.M.E., Maier-Reimer, E., 2005. Causes of marine productivity and oxygen changes associated with the Permian-Triassic boundary: A reevalution with ocean general circulation models. Mar. Geol. 217, 283-304.

Winguth, C., Winguth, A.M.E., 2012. Simulating Permian-Triassic oceanic anoxia distribution: Implications for species extinction and recovery. Geology 40, 127-130.

Yin, H.F., Xie, S.C., Luo, G.M., Algeo, T.J., 2012. Episodic environmental changes at the Permian-Triassic boundary of Meishan. Episodes, in press.

Zhao, L., Chen, Z.Q., Algeo, T.J., Chen, J.P., Chen, Y.L., Tong, J. N ., Gao, S., Zhou, L., Hu, Z., and Liu, Y.S., 2012. Rare-earth element patterns in conodont albid crowns: evidence for massive inputs of volcanic ash following the latest Permian mass extinction? Global and Planetary Change, in press.

Last updated 17 Sept 2012

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