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]
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]
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]
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]