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    Mercury isotope evidence for marine photic zone euxinia across the end-Permian mass extinction
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    Abstract:
    Abstract The driving forces, kill and recovery mechanisms for the end-Permian mass extinction (EPME), the largest Phanerozoic biological crisis, are under debate. Sedimentary records of mercury enrichment and mercury isotopes have suggested the impact of volcanism on the EPME, yet the causes of mercury enrichment and isotope variations remain controversial. Here, we model mercury isotope variations across the EPME to quantitatively assess the effects of volcanism, terrestrial erosion and photic zone euxinia (PZE, toxic, sulfide-rich conditions). Our numerical model shows that while large-scale volcanism remains the main driver of widespread mercury enrichment, the negative shifts of Δ 199 Hg isotope signature across the EPME cannot be fully explained by volcanism or terrestrial erosion as proposed before, but require additional fractionation by marine mercury photoreduction under enhanced PZE conditions. Thus our model provides further evidence for widespread and prolonged PZE as a key kill mechanism for both the EPME and the impeded recovery afterward.
    Keywords:
    Mercury
    Mass-independent fractionation
    Permian–Triassic extinction event
    Abstract The biggest known mass extinction in the history of animal life occurred at the Permian–Triassic boundary and has often been linked to global warming. Previous studies have suggested that a geologically rapid (<40 kyr) temperature increase of more than 10°C occurred simultaneously with the main extinction pulse. This hypothesis is challenged by geochemical and palaeontological data indicating profound environmental perturbations and a temperature rise prior to the main extinction. Using secondary ion mass spectrometry (SIMS), we measured oxygen isotope ratios from Changhsingian (late Permian) ostracods of north‐western Iran. Our data show that ambient seawater temperature began to rise at least 300 kyr prior to the main extinction event. Gradual warming by approximately 12°C was probably responsible for initial environmental degradation that eventually culminated in the global end‐Permian mass extinction.
    Permian–Triassic extinction event
    Extinction (optical mineralogy)
    Citations (11)
    Significance To understand how most life on Earth went extinct 250 million years ago, we used multiple sulfur isotopes to investigate redox chemistry changes in the Panthalassic Ocean, comprising ∼85–90% of the contemporaneous global ocean. The S-isotopic anomalies from Canada and Japan provide evidence for the timing of the onset of euxinia and mixing of sulfidic and oxic waters. Our data suggest that shoaling of H 2 S-rich waters may have driven the mass extinction and delayed the recovery of the marine ecosystem. This study illustrates how environmental changes could have had a devastating effect on Earth’s early biosphere, and may have present-day relevance because global warming and eutrophication are causing development of sulfidic zones on modern continental shelves, threatening indigenous marine life.
    Permian–Triassic extinction event
    Early Triassic
    Extinction (optical mineralogy)
    Citations (71)
    Abstract The end‐Permian mass extinction was the most pervasive biotic crisis in the history of life. About 80% of marine species and some 70% of land species became extinct, probably in two pulses separated by about 10 million years.
    Permian–Triassic extinction event
    Extinction (optical mineralogy)
    Citations (1)
    Significance The end of the Triassic Period (∼201.5 million years ago) witnessed one of the largest mass extinctions of animal life known from Earth history. This extinction is suggested to have coincided with and been caused by one of the largest known episodes of volcanic activity in Earth’s history. This study examines mercury concentrations of sediments from around the world that record this extinction. Mercury is emitted in gaseous form during volcanism, and subsequently deposited in sediments. We find numerous pulsed elevations of mercury concentrations in end-Triassic sediments. These peaks show that the mass extinction coincided with large-scale, episodic, volcanism. Such episodic volcanism likely perturbed the global environment over a long period of time and strongly delayed ecological recovery.
    Mercury
    Extinction (optical mineralogy)
    Geologic record
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    Abstract The end-Permian mass extinction occurred alongside a large swath of environmental changes that are often invoked as extinction mechanisms, even when a direct link is lacking. One way to elucidate the cause(s) of a mass extinction is to investigate extinction selectivity, as it can reveal critical information on organismic traits as key determinants of extinction and survival. Here we show that machine learning algorithms, specifically gradient boosted decision trees, can be used to identify determinants of extinction as well as to predict extinction risk. To understand which factors led to the end-Permian mass extinction during an extreme global warming event, we quantified the ecological selectivity of marine extinctions in the well-studied South China region. We find that extinction selectivity varies between different groups of organisms and that a synergy of multiple environmental stressors best explains the overall end-Permian extinction selectivity pattern. Extinction risk was greater for genera that had a low species richness, narrow bathymetric ranges limited to deep-water habitats, a stationary mode of life, a siliceous skeleton, or, less critically, calcitic skeletons. These selective losses directly link the extinctions to the environmental effects of rapid injections of carbon dioxide into the ocean–atmosphere system, specifically the combined effects of expanded oxygen minimum zones, rapid warming, and potentially ocean acidification.
    Permian–Triassic extinction event
    Extinction (optical mineralogy)
    Citations (16)
    The Permian/Triassic mass extinction plays a great role in the evolutionary history of the Earth.After that,the revolution of species was accelerated greatly.The paper summarizes simply the research results of geochemists,geologists and paleontologists in recent years,including dating of the event and several hypotheses.Especially,we described in detail the exterrestrial impact(asteroid or comet),volcanic eruption,anoxia and marine acidification,and then made a simple analysis and discussion in the significance of mass extinction.
    Permian–Triassic extinction event
    Early Triassic
    Extinction (optical mineralogy)
    Trias
    Citations (0)
    The end-Permian mass extinction is the greatest bioevent in the geological history, which wiped out nearly 95% of the marine species and 75% of the terrestrial species,followed by a biological winter for more than five million years.The cause and the process of the end-Permian mass extinction remain an unsolved mystery in earth science and one of the most difficult and interesting scientific problems.
    Permian–Triassic extinction event
    Extinction (optical mineralogy)
    Citations (0)