Cause Of Mass Extinction Research Articles

Mass extinctions in Phanerozoic time

Abstract Following publication in 1980 of the celebrated paper in Science ( 208 , 1095–1108) by Luis Alvarez and his colleagues, a widespread interest developed in the possibility that bolide impact was a major if not indeed the most important cause of mass extinctions in the Phanerozoic. Of particular interest was the claim of a 26 Ma extinction periodicity in the last 250 Ma, which led to suggestions of ultimate astronomical control. Intensive research subsequently casts serious doubt on such a periodicity, and the only really persuasive evidence associating impact with mass extinction is that at the Cretaceous-Tertiary boundary. It is generally accepted that there were five major episodes of mass extinction in the Phanerozoic record: end-Ordovician, late Devonian (Frasnian-Famennian boundary), end-Permian, end-Triassic and end-Cretaceous. In addition a number of lesser events have been widely recognized, most notably at the Devonian-Carboniferous, Cenomanian-Turonian and Paleocene-Eocene boundaries, and in the early Toarcian. The extinction record is based essentially on marine invertebates, and the evidence from terrestrial vertebrates is far less clear, with the exception of dinosaurs at the Cretaceous-Tertiary boundary. Although it has been maintained that terrestrial plants were not subjected to mass extinction episodes there is abundant evidence for at least extensive regional extinction events, most notably at the Permian-Triassic, Triassic-Jurassic and Cretaceous-Tertiary boundaries. Only a small number of factors can plausibly be invoked to account for environmental perturbations on a global scale, of the sort that could significantly increase extinction rate: bolide impact, volcanism, climatic cooling, climatic warming, marine regression and marine transgression with the accompanying spread of anoxic bottom waters. Good evidence for bolide impact, in the form of significant iridium anomalies on a global scale, and shocked quartz coincident with mass extinction, is only available for the end-Cretaceous event, and a likely impact crater has been identified in the Yucatan Peninsula of Mexico. Microtektites have been recognized both in Upper Devonian and Upper Eocene strata, but their horizons do not coincide with mass extinction events. Claims for impact at the end of the Triassic, based on purported shocked quartz, are decidedly dubious. The only good correlation with large-scale flood basalt volcanism is for the end-Permian and end-Cretaceous events, respectively the Siberian and Deccan Traps, but any causal correlation is more likely than not to involve climate. Climatic cooling is strongly implicated only for the latest Ordovician and late Eocene to Oligocene, and climatic warming episodes, as in the earliest Silurian, Triassic and Eocene, were probably at least as important. Marine regression caused by sea-level fall correlates well with extinction events in the late early Cambrian, end-Ordovician, late Permian, end-Triassic and end-Cretaceous. More important than any other factor, anoxia and transgression appear to be strongly associated with events in the late early Cambrian, late Cambrian, earliest Silurian, Frasnian-Famennian and Devonian-Carboniferous boundaries, Permian-Triassic, Cenomanian-Turonian and Paleocene-Eocene boundaries, and early Toarcian. Often, of course, more than one factor may be implicated, one of the most striking associations being between episodes of marine transgression-anoxia and climatic warming. Such environmental changes could clearly affect both marine and terrestrial organisms simultaneously. Even if one accepts bolide impact as a major causal factor for the end-Cretaceous extinctions, its environmental effects are still controversial and difficult to disentangle from those caused by phenomena intrinsic to our planet. Arguments persists among palaeontologists about how catastrophic the mass extinction was.

Size changes of bivalves and a hypothesis about the cause of mass extinction

Size changes of bivalves and a hypothesis about the cause of mass extinction

Permian-Triassic mass extinction event recorded in bedded chert sequence in southwest Japan

Rock types in southwest Japan change across the Permian-Triassic boundary. Late Permian bedded chert grades upward into latest Permian siliceous claystone, carbonaceous mudstone of unknown age, early Triassic siliceous claystone with carbonaceous mudstone and chert interbeds, and then into middle Triassic to Jurassic bedded chert. These stratigraphic lithologic variation also accompany the decline and recovery of radiolarians in the Changxingian stage and Smithian stage, respectively. The Permian-Triassic boundary is not precisely defined because of poor stratigraphic control, but it is thought to occur at the boundary between the carbonaceous mudstone and the Changxingian siliceous claystone, or somewhere in the carbonaceous mudstone. During the Griesbachian stage there was deposition of carbonaceous mudstone in deep pelagic seas. Bioturbation structures and the massive nature of carbonaceous mudstone indicate dysaerobic, but not anoxic condition in a strict sense. The dramatic decrease in productivity of radiolarians preceded the sedimentation of carbonaceous mudstone, which suggests that oxygen-deficient conditions were not the primary cause of mass extinction. Red tide-type conditions inferred from the increased primary productivity in the pelagic seas and the oxygen deficiency in the epicontinental seas are the last hit against the biosphere in the chain of events that started from late Permian and caused the greatest mass extinction of the Phanerozoic. Correlation between lithologic variations of bedded cherts and δ13C excursions of carbonate rocks clarifies the processes of simultaneous massive decline and recovery of biomass as represented in both group of rocks.

Implications of the infra- and inter-trappean biota from the Deccan, India, for the role of volcanism in Cretaceous-Tertiary boundary extinctions

The fossil record shows a remarkable similarity between the biota that existed before and after the initiation of Deccan volcanic activity. Virtually all the available palaeontological evidence, such as the fauna and flora of the freshwater infra- and inter-trappean beds and the planktonic foraminifera from the subsurface infra- and inter-trappean beds of the southeastern coast, do not favour the initiation of Deccan volcanism as the cause of mass extinctions at the Cretaceous-Tertiary (K-T) boundary. Instead, a combination of events, such as an extended period of volcanism, changes in sea-level and related climatic changes, and certain local factors, may have played a significant role in selectively eliminating various groups of organisms. This view is further reinforced by the biotic changes across the K-T iridium layer in the Um Sohryngkew River section of Meghalaya, northeastern India.

Extinction of dinosaurs: A possible novel cause

A novel cause of mass extinction of fauna close to the (K/T) Boundary is suggested. A large amount of non-protein amino acids (AIB and ISOVAL) has been observed close to this event. It is speculated that these amino acids may be toxic and are responsible for the extinction. The toxicity level is estimated for this suggestion to be true and experimentalists are encouraged to test this level of toxicity for the amino acids.

Common Patterns of Mass Extinction, Survival, and Recovery in Marine Environments: What Do They Tell Us About the Future?

Mass extinction is characterized by the loss of more than 50 percent of the world's species within a short interval of geologic time - months to as much as 3 million years (My). In the fossil record, these events have primarily been recorded from the marine realm. Three patterns of mass extinction have been described - catastrophic, stepwise, and graded extinction. Many well-studied extinction intervals contain elements of more than one pattern, suggesting that these biotic crises were caused by varied forcing mechanisms linked by complex environmental feedback loops. This hypothesis is supported by the discovery that the four well-studied Phanerozoic mass extinctions (Late Devonian, middle and terminal Cretaceous, Eocene-Oligocene boundary extinctions) share a number of physical, chemical, and biological characteristics in common. They consistently show stepwise extinction patterns linked to intervals of extraordinary fluctuations in the temperature, chemistry and structure of ocean-climate systems, at rates and magnitudes well above background levels. In addition, tropical ecosystems were the first and most severely affected, and more poleward, temperate biotas were mainly stressed during the later phases of the extinction interval. Evidence for these unusual environmental changes is derived from high-resolution (cm-scale) paleobiological, sedimentological, trace-element and stable-isotope analyses spanning mass extinction intervals. These dramatic environmental fluctuations were the immediate causes of mass extinction, as they progressively exceeded the survival limits of global biotas largely adapted to warm, equable, ice-free climates which characterized over 90 percent of Phanerozoic time. These environmental fluctuations probably represented feedback phenomena from more powerful, short-term forcing mechanisms which abruptly perturbed the structure of ocean-climate systems. Multiple impacts of extraterrestrial objects within short (<1-3 My) time intervals - so-called meteorite/comet showers - are the most logical candidates. This hypothesis is supported by physical and chemical evidence for impacts clustered around most, but not all, Mesozoic and Cenozoic mass extinctions.

Testing for causal relationships between large pyroclastic volcanic eruptions and mass extinctions

The Permo/Triassic mass extinction, the most extensive of all Phanerozoic extinctions [Erwin, 1990], has been correlated with both massive pyroclastic eruptions [Yang and Yin, 1987; Yin et al., 1989; Jinwen, 1989] and flood basalts [Rampino and Strothers, 1988]. More tentatively, the end‐Cretaceous mass extinction has also been linked with massive volcanic events [Officer et al, 1987; Rampino and Strothers, 1988]. However, the nature of the connection between volcanism and either mass extinction remains uncertain. Rather than study volcanic events at known extinction horizons, another approach is to identify extremely large (>1000 km3) pyroclastic eruptions with well‐constrained age determinations, and evaluate the fossil record for evidence of significant regional or global extinctions. We selected the largest, best constrained pyroclastic events known, (Toba Tuff, Huckleberry Ridge Tuff, Tuff of Blacktail and the Elkhorn Mountain volcanics); neither global marine diversity nor global or regional terrestrial vertebrate diversity exhibit any biological effect from these extremely massive pyroclastic eruptions. We conclude that massive pyroclastic eruptions are unlikely to have been an effective cause of mass extinctions.

Lessons from mass extinction

A session on the Mass Extinction Debates will be held July 12 at the Biannual Meeting of the International Society for the History, Philosophy, and Social Studies of Biology at Northwestern University. This meeting will be the first that brings together the debating scientists with historians, philosophers, and sociologists of science who view the extinction upheaval as an exceptional opportunity to observe the workings of science that may be hidden from view in the study of less controversial topics.The growing debates over the cause of mass extinctions were triggered by the Alvarez/Berkeley‐group meteorite impact hypothesis in 1979. The conflict has engaged a seemingly broader range of scientific disciplines than any other debate in the history of Earth sciences and has prompted rejuvenation of long quiescent areas of research, collaborations between formerly isolated specialists, redirection of careers, and remarkable new field studies, experiments, and reexamination of evidence.

ジオカタストロフィー 生物の絶滅と地球磁場の逆転

One of the most interesting paleontological contributions to general knowledge is evidence that once-dominant giant reptiles died out in the end of the Cretaceous period. Recently, on the basis of the iridium enrichment in Cretaceous-Tertiary (K-T) boundary layers, the Berkeley research group suggested that the process of mass extinction of species is extraterrestrial in origin, probably caused by the impact of large meteorites on the Earth. Since this suggestion, it has become fashionable for geochemists to discover an iridium abundance at K-T boundary sites or at other mass-extinction horizons around the world.Many Earth- and planet-scientists have eagerly discussed on the possibilities of a global catastrophe due to bolide impacts. The probability of striking the Earth by an Earth-crossing asteroid is estimated to be not no small. As a matter of fact, in January 18, 1991, astronomical observations found a small asteroid crossing the Earth's orbit within half the distance to the Moon. Earth-crossing comets are even more plentiful. The probability of comet collisions to the Earth is supposed to increase extremely when the Solar System encounters with a dense molecular cloud in the Galaxy.Some volcanologists protest against the impact hypothesis, insisting that a bolide impact is not the only way to cause a global catastrophe. Despite that a large-scale volcanic eruption can produce iridium enrichments, the presence of shock quartz at K-T boundary sites remains a problem for proponents of volcanism. It seems that the extraterrestrial-origin hypothesis has advantage over the volcanic hypothesis. Various hypotheses of mass extinction are reviewed in the first half of this paper.It is a well-known fact that the Earth's magnetic field has repeatedly flip-flopped. The great circulation of molten iron in the Earth' core generates the geomagnetic field. The sophisticated theory of electromagnetic fluid dynamics explains the mechanism of the geomagnetic generation, but there still remain uncertainties in the mechanism of geomagnetic reversal. Some paleomagneticians speculated that the asteroid impact is an immediate cause of geomagnetic reversal, but others rejected the idea of such a linkage from standpoints of microtektite studies.Recently, a Japanese research group has analyzed samples of sedimentary rock, whose sedimentation rate was 3 m/ka during the Matuyama-Brunhes reversal period, and discovered changes in both oxygen and carbon isotope ratios coincident with reversal. The decrease in carbon isotope ratio of 1 permill corresponds supposedly to the 40 % reduction of biomass, which indicates a large amount of CO2 gas flows into the ocean and the atmosphere from the biosphere. The concurrent decrease in oxygen isotope ratio can be explained as the CO2-induced greenhouse effect.The coincidence of a biomass changes with a geomagnetic reversal implies that the reversal may be one of possible causes of mass extinction. The biosphere is protected by the shield effect of magnetic field against solar high-energy particles. During the time of reversal when the shield effect disappears, the biosphere may be directly exposed to harmful ultraviolet ray and further affected by the concurrently-occurred global climate change. On the basis of observational facts that the geomagnetic dipole moment has been rapidly decreasing, many geomagneticians give a warning that the Earth is now standing at the starting point of a magnetic reversal. If the decrease will continue as it is, the geomagnetic field will completely disappear in one thousand years or later.

The Great Dying: Cosmic Catastrophe, Dinosaurs, and the Theory of Evolution

As the subtitle of this well written, informative book suggests, current ideas on the causes of mass extinction as resulting from bolloide impact intertwine with the subsequent impact of these ideas on evolutionary theory.The book begins with the author's strongly stated objections to the natural selection theory. He rejects it on the ground that it is non‐falsifiable and therefore non‐scientific. He points out that the question of whether or not natural selection is a proper scientific theory is more than a matter of academic interest because many horrors of the past century perpetrated on one group of the human race by another have sought partial justification through appeal to the theory.

Snowbird II: Global catastrophes

Recently, on a National Public Radio retrospective on American life a quarter‐century ago, a commentator remarked that 1963 was one of the last years when we knew that the dinosaurs died out “because they were stupid, just plain too stupid,” and not due to some exotic mechanism. In 1989, catastrophic causes still reign supreme. Yet, in the public's mind, the controversy has not yet been settled: was it an asteroid, explosive volcanism, or a comet shower? Technical debates have raged since the late Luis Alvarez, his son Walter, and their Berkeley coworkers distributed preprints nearly a decade ago of their seminal paper [Alvarez et al., 1980] on the extraterrestrial cause for mass extinctions at the end of the Cretaceous Period. A recent conference, Global Catastrophes in Earth History, has shown that the debate is now mainly over. The meeting was held October 20–22, 1988, at Snowbird, Utah, and hereafter I refer to it as the “Snowbird II meeting.”

Organic-chemical clues to the theory of impacts as a cause of mass extinctions

The reasons for the mass extinctions, which occur from time to time in Earth's history-as, e.g., the dinosaur extinction at the Cretaceous/Tertiary boundary 65 myr ago - are still not satisfactorily cleared up. A possible reason might be the impact of one or several comets of several kilometers in diameter. In this paper the astrophysical background of this hypothesis and organic-chemical processes during an impact will be discussed. Quantitative estimations are given, which show that the amount of organic substances brought to the Earth may be of the same order of magnitude as the normal biological production of organic material. Investigations are proposed to examine the organic-chemical composition of profiles of the Cretaceous/Tertiary boundary and other boundaries, at which mass extinction had occurred, in order to find anomalies as consequences of impacts.

Comet showers as a cause of mass extinctions

If at least some mass extinctions are caused by impacts, why do they extend over intervals of one to three million years and have a partly stepwise character? The solution may be provided by multiple cometary impacts. Astronomical, geological and palaeontological evidence is consistent with a causal connection between comet showers, clusters of impact events and stepwise mass extinctions, but it is too early to tell how pervasive this relationship may be.

Some Implications of Mass Extinction for the Evolution of Complex Life

Extinction has the destructive effect of eliminating established lineages from an evolutionary system and the constructive effect of vacating ecospace into which new lineages can evolve. Mass extinctions, which are times of unusually intense extinction, have been consistently followed by major radiations of new lineages. Extraterrestrial impacts associated with extinction events and a periodic recurrence of these events implicates an extraterrestrial forcing mechanism as the ultimate cause of mass extinction. This suggests that the extraplanetary environment has played an important, active role in the development of complex life on Earth.

Effects of intense stratospheric ionisation events

High levels of ionising radiation in the Earth's stratosphere will lead to increased concentrations of nitrogen oxides and decreased concentrations of ozone. Changes in the surface environment will include an increased level of biologically harmful UV radiation, caused by the ozone depletion, and a decreased level of visible solar radiation, due to the presence of major enhancements in the stratospheric concentration of nitrogen dioxide. These changes are studied quantitatively, using the passage of the Solar System through a supernova remnant shell as an example. Some of the potential environmental changes are a substantial global cooling, abnormally dry conditions, a reduction in global photosynthesis and a large increase in the flux of atmospheric fixed nitrogen to the surface of the Earth. Such events might have been the cause of mass extinctions in the distant past.

A Natural Experiment to Test the Hypothesis That Loss of Genetic Variability was Responsible for Mass Extinctions of the Fossil Record

Animals living under "constant" environmental conditions have been hypothesized to lose genetic variability. If so, this would account for a lack of adaptation to changing environments and hence be responsible for the significant mass extinctions of the fossil record. However, eight modern deep-sea species (1,000-2,000 m) in as constant a major environment as exists on earth, have as much genetic variability as do shallow marine and terrestrial species (20%-50% of the loci polymorphic). Accordingly, species do not appear to lose genetic variability as the environment becomes "constant," and this explanation of the cause for mass extinction fails.