ABSTRACT
The end-Permian extinction is associated with a mysterious disruption to Earth's carbon cycle. Here we identify causal mechanisms via three observations. First, we show that geochemical signals indicate superexponential growth of the marine inorganic carbon reservoir, coincident with the extinction and consistent with the expansion of a new microbial metabolic pathway. Second, we show that the efficient acetoclastic pathway in Methanosarcina emerged at a time statistically indistinguishable from the extinction. Finally, we show that nickel concentrations in South China sediments increased sharply at the extinction, probably as a consequence of massive Siberian volcanism, enabling a methanogenic expansion by removal of nickel limitation. Collectively, these results are consistent with the instigation of Earth's greatest mass extinction by a specific microbial innovation.
Subject(s)
Biological Evolution , Extinction, Biological , Geologic Sediments/chemistry , Metabolic Networks and Pathways/physiology , Methane/biosynthesis , Methanosarcina/genetics , Volcanic Eruptions/history , Carbon Cycle/physiology , Carbon Isotopes/analysis , China , History, Ancient , Methanosarcina/physiology , Nickel/analysis , Oceans and Seas , Phylogeny , RNA, Ribosomal, 16S/genetics , Volcanic Eruptions/adverse effectsABSTRACT
The end-Permian mass extinction was the most severe biodiversity crisis in Earth history. To better constrain the timing, and ultimately the causes of this event, we collected a suite of geochronologic, isotopic, and biostratigraphic data on several well-preserved sedimentary sections in South China. High-precision U-Pb dating reveals that the extinction peak occurred just before 252.28 ± 0.08 million years ago, after a decline of 2 per mil () in δ(13)C over 90,000 years, and coincided with a δ(13)C excursion of -5 that is estimated to have lasted ≤20,000 years. The extinction interval was less than 200,000 years and synchronous in marine and terrestrial realms; associated charcoal-rich and soot-bearing layers indicate widespread wildfires on land. A massive release of thermogenic carbon dioxide and/or methane may have caused the catastrophic extinction.
Subject(s)
Biodiversity , Ecosystem , Extinction, Biological , Fossils , Animals , Carbon Dioxide , Carbon Isotopes , China , Fires , Geologic Sediments , Invertebrates/classification , Isotopes , Lead , Mass Spectrometry , Methane , Oceans and Seas , Plants/classification , Radioisotope Dilution Technique , Radiometric Dating , Seawater/chemistry , Time , Uranium , Vertebrates/classificationABSTRACT
Carbon and sulfur isotopic data, together with biomarker and iron speciation analyses of the Hovea-3 core that was drilled in the Perth Basin, Western Australia, indicate that euxinic conditions prevailed in the paleowater column during the Permian-Triassic superanoxic event. Biomarkers diagnostic for anoxygenic photosynthesis by Chlorobiaceae are particularly abundant at the boundary and into the Early Triassic. Similar conditions prevailed in the contemporaneous seas off South China. Our evidence for widespread photiczone euxinic conditions suggests that sulfide toxicity was a driver of the extinction and a factor in the protracted recovery.
