Английская Википедия:End-Botomian mass extinction

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The end-Botomian mass extinction event, also known as the late early Cambrian extinctions, refer to two extinction intervals that occurred during Stages 4 and 5 of the Cambrian Period, approximately 513 to 509 million years ago. Estimates for the decline in global diversity over these events range from 50% of marine genera[1] up to 80%.[2] Among the organisms affected by this event were the small shelly fossils, archaeocyathids (an extinct group of sponges), trilobites, brachiopods, hyoliths, and mollusks.[1][3][4][5]

Causes

There are several hypotheses for the causes of these extinctions. There is evidence that major changes in the carbon cycle[6][7][8][9] and sea level occurred during this time.[1][10] Evidence also exists for the development of anoxia (a loss of oxygen) in some environments in the oceans.[1][11][12]

One hypothesis that unifies this evidence links these environmental changes to widespread volcanic eruptions caused by the emplacement of the Kalkarindji Large Igneous Province or LIP.[13][14] These widespread eruptions would have injected large amounts of greenhouse gases into the atmosphere causing warming of the climate and subsequent acidification and loss of oxygen in the oceans.[13] Mercury anomalies have been discovered in strata corresponding to the extinction event; however, such enrichments in mercury are also found in older rocks that predate the biotic crisis.[15] The precise timing between the eruptions and the extinction events remain unresolved.[14]

References

Шаблон:Reflist

External links