Below are a few sources I found from my initial search. I've included their citation information and abstracts, and they are all peer-reviewed articles.
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Berner, Robert A. “Examination of hypotheses for the Permo-Triassic boundary extinction by carbon cycle modeling.” Proceedings of the National Academy of Sciences of the United States of America. 99.7 (2002); 4172-4177.
Abstract:
The biological extinction that occurred at the Permian-Triassic boundary represents the most extensive loss of species of any known event of the past 550 million years. There have been a wide variety of explanations offered for this extinction. In the present paper, a number of the more popular recent hypotheses are evaluated in terms of predictions that they make, or that they imply, concerning the global carbon cycle. For this purpose, a mass balance model is used that calculates atmospheric CO sub(2) and oceanic delta super(13)C as a function of time. Hypotheses considered include: (i) the release of massive amounts of CO sub(2) from the ocean to the atmosphere resulting in mass poisoning; (ii) the release of large amounts of CO sub(2) from volcanic degassing; (iii) the release of methane stored in methane hydrates; (iv) the decomposition and oxidation of dead organisms to CO sub(2) after sudden mass mortality, and (v) the long-term reorganization of the global carbon cycle. The modeling indicates that measured short-term changes in delta super(13)C at the boundary are best explained by methane release with mass mortality and volcanic degassing contributing in secondary roles. None of the processes result in excessively high levels of atmospheric CO sub(2) if they occurred on time scales of more than about 1,000 years. The idea of poisoning by high levels of atmospheric CO sub(2) depends on the absence of subthermocline calcium carbonate deposition during the latest Permian. The most far-reaching effect was found to be reorganization of the carbon cycle with major sedimentary burial of organic matter shifting from the land to the sea, resulting in less burial overall, decreased atmospheric O sub(2), and higher atmospheric CO sub(2) for the entire Triassic Period.
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Isozaki, Y. & Shimizu, N. “End-Permian extinction and volcanism-induced environmental stress: The Permian-Triassic Boundary interval of lower-slope facies at Chaotian, South China.” Palaeogeography, Palaeoclimatology, Palaeoecology. 252.1-2 (2007); 218-238.
Abstract:
In order to reveal environmental changes across the Permo-Triassic boundary (PTB), the detailed lithostratigraphy of the PTB interval is analyzed at Chaotian in northern Sichuan, China. The studied section is composed of the Changhsingian (Upper Permian) Dalong Formation and the Induan (Lower Triassic) Feixianguan Formation of a lower-slope facies deposited on the northwestern margin of the Yangtze carbonate platform. The 12-m-thick interval across the PTB consists mainly of bedded carbonates and mudstone, and is lithologically divided into 7 units, i.e., Units A to G, in ascending order. The main extinction horizon of Permian taxa is recognized at the Unit D/E boundary where various fossil metazoans and protists, such as ammonoids, brachiopods, bivalves, conodonts, and radiolarians, rapidly disappeared or became scarce. The complete disappearance of radiolarians at the Unit D/E boundary emphasizes that the PTB extinction affected not only various Late Permian benthic and free-swimming metazoans but also planktonic protozoans. The lowest Induan index conodont Hindeodus parvus first occurs at the base of Unit F, marking the biostratigraphically defined PTB horizon. Unit E composed of unique bedded marl between the main extinction horizon and the first occurrence of Triassic taxon represents a period of strong environmental stresses that suppressed productivity both of silica- and carbonate-secreting organisms. By changing their size, radiolarians reacted most sensitively to the environmental change that already started in the late Changhsingian, appreciably before the final extinction event. The frequent intercalation of rhyo-dacitic tuff beds, particularly in Unit D and the lower part of Unit E across the main extinction horizon, suggests that intermittent felsic volcanism and relevant environmental change may have been responsible for the mass extinction of the Permian taxa and for the prolonged post-extinction lag time before the initial recovery. The frequent ash falls during the late Changhsingian indicate that the volcanism-induced environmental change had already started earlier than the main extinction. All the biological production (carbonate, silica, and organic matter) collapsed at the Unit D/E boundary when the environmental stresses may have passed a critical threshold for maintaining ecological stability. The PTB interval between the extinction and the first appearance of Triassic taxon at Chaotian is ca. 1.4 m thick, apparently almost eight times thicker than that at the Global Stratotype Section and Point of PTB in Meishan (19 cm). The Chaotian section, as well as the neighboring Shangsi section in northern Sichuan, may provide a better chance for high-resolution chemostratigraphic analyses that may allow detection and correlation of subtle environmental changes across the PTB.
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Kidder, D. L. & Worsley, T. R. “Causes and consequences of extreme Permo-Triassic warming to globally equable climate and relation to the Permo-Triassic extinction and recovery.” Palaeogeography, Palaeoclimatology, Palaeoecology. 203.3-4 (2004); 207-237.
Abstract:
Permian waning of the low-latitude Alleghenian/Variscan/Hercynian orogenesis led to a long collisional orogeny gap that cut down the availability of chemically weatherable fresh silicate rock resulting in a high-CO2 atmosphere and global warming. The correspondingly reduced delivery of nutrients to the biosphere caused further increases in CO2 and warming. Melting of polar ice curtailed sinking of O2- and nutrient-rich cold brines while pole-to-equator thermal gradients weakened. Wind shear and associated wind-driven upwelling lessened, further diminishing productivity and carbon burial. As the Earth warmed, dry climates expanded to mid-latitudes, causing latitudinal expansion of the Ferrel circulation cell at the expense of the polar cell. Increased coastal evaporation generated O2- and nutrient-deficient warm saline bottom water (WSBW) and delivered it to a weakly circulating deep ocean. Warm, deep currents delivered ever more heat to high latitudes until polar sinking of cold water was replaced by upwelling WSBW. With the loss of polar sinking, the ocean was rapidly filled with WSBW that became increasingly anoxic and finally euxinic by the end of the Permian. Rapid incursion of WSBW could have produced similar to 20 m of thermal expansion of the oceans, generating the well-documented marine transgression that flooded embayments in dry, hot Pangaean mid-latitudes. The flooding further increased WSBW production and anoxia, and brought that anoxic water onto the shelves. Release of CO2 from the Siberian traps and methane from clathrates below the warming ocean bottom sharply enhanced the already strong greenhouse. Increasingly frequent and powerful cyclonic storms mined upwelling high-latitude heat and released it to the atmosphere. That heat, trapped by overlying clouds of its own making, suggests complete breakdown of the dry polar cell. Resulting rapid and intense polar warming caused or contributed to extinction of the remaining latest Permian coal forests that could not migrate any farther poleward because of light limitations. Loss of water stored by the forests led to aquifer drainage, adding another similar to 5 m to the transgression. Non-peat-forming vegetation survived at the newly moist poles. Climate feedback from the coal-forest extinction further intensified warmth, contributing to delayed biotic recovery that generally did not begin until mid-Triassic, but appears to have resumed first at high latitudes late in the Early Triassic. Current quantitative models fail to generate high-latitude warmth and so do not produce the chain of events we outline in this paper. Future quantitative modeling addressing factors such as polar cloudiness, increased poleward heat transport by deep water and its upwelling by cyclonic storms, and sustainable mid-latitude sinking of warm brines to promote anoxia, warming, and thermal expansion of deep water may more closely simulate conditions indicated by geological and paleontological data.
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Knoll, A.H. & Bambach, R.K. “Paleophysiology and end-Permian mass Extinction.” Earth and Planetary Science Letters. 256.3-4 (2007); 295-313.
Abstract:
Physiological research aimed at understanding current global change provides a basis for evaluating selective survivorship associated with Permo-Triassic mass extinction. Comparative physiology links paleontological and paleoenvironmental observations, supporting the hypothesis that an end-Permian trigger, most likely Siberian Trap volcanism, touched off a set of physically-linked perturbations that acted synergistically to disrupt the metabolisms of latest Permian organisms. Global warming, anoxia, and toxic sulfide probably all contributed to end-Permian mass mortality, but hypercapnia (physiological effects of elevated P sub(C) sub(O) sub(2)) best accounts for the selective survival of marine invertebrates. Paleophysiological perspectives further suggest that persistent or recurring hypercapnia/global warmth also played a principal role in delayed Triassic recovery. More generally, physiology provides an important way of paleobiological knowing in the age of Earth system science.
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Xie, Shucheng. & Pancost, Richard. “Molecular and isotopic evidence for episodic environmental change across the Permo/Triasic Boundary at Meishan in South China.” Global and Planetary Change. 55.1-3 (2007); 56-65.
Abstract:
Lipid biomarker abundances and delta 13C values were determined across the Permian-Triassic (P-Tr) boundary at Meishan of southern China. The delta 13C values of n-alkanes showed large (9) fluctuations, which suggest major episodic changes in oceanographic conditions during faunal mass extinctions. Environment-related biomarker ratios, including pristane to phytane ratios (Pr/Ph), gammacerane to C31 homohopane ratios ( gamma /C31HP) and C27 18 alpha (H)-22,29,30-trinorneohopane to C27 17 alpha (H)-22,29,30-trinorhopane ratios (Ts/Tm), vary extensively throughout the section, with values typically associated with anoxic conditions coinciding with maximum delta 13C values. In particular, both faunal mass extinction horizons (beds 25 and 28) are characterised by biomarker ratios consistent with anoxic conditions and elevated n-alkane delta 13C values. The records of environment-related biomarkers and n-alkane delta 13C values clearly signify multiple environmental perturbations in association with faunal mass extinctions.
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