Impact Ejecta Layer from the Mid-Devonian: Possible Connection to Global Mass Extinctions

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Science  13 Jun 2003:
Vol. 300, Issue 5626, pp. 1734-1737
DOI: 10.1126/science.1081544

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We have found evidence for a bolide impacting Earth in the mid-Devonian (∼380 million years ago), including high concentrations of shocked quartz, Ni, Cr, As, V, and Co anomalies; a large negative carbon isotope shift (–9 per mil); and microspherules and microcrysts at Jebel Mech Irdane in the Anti Atlas desert near Rissani, Morocco. This impact is important because it is coincident with a major global extinction event (Kacák/otomari event), suggesting a possible cause-and-effect relation between the impact and the extinction. The result may represent the extinction of as many as 40% of all living marine animal genera.

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