Postimpact earliest Paleogene warming shown by fish debris oxygen isotopes (El Kef, Tunisia)

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Science  29 Jun 2018:
Vol. 360, Issue 6396, pp. 1467-1469
DOI: 10.1126/science.aap8525

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Warming after the big one

The Chicxulub impact 65 million years ago, which caused the mass extinction at the Cretaceous-Paleogene boundary, also initiated a long period of strong global warming. Using data from phosphatic microfossils, including fish teeth, scales, and bone, MacLeod et al. estimated global average temperature. Immediately after the asteroid strike, temperatures increased by ∼5°C and remained high for about 100,000 years (see the Perspective by Lécuyer). These results are relevant to current climate projections, because the Chicxulub impact perturbed Earth systems on time scales even shorter than the current rate of change.

Science, this issue p. 1467; see also p. 1400


Greenhouse warming is a predicted consequence of the Chicxulub impact, but supporting data are sparse. This shortcoming compromises understanding of the impact’s effects, and it has persisted due to an absence of sections that both contain suitable material for traditional carbonate- or organic-based paleothermometry and are complete and expanded enough to resolve changes on short time scales. We address the problem by analyzing the oxygen isotopic composition of fish debris, phosphatic microfossils that are relatively resistant to diagenetic alteration, from the Global Stratotype Section and Point for the Cretaceous/Paleogene boundary at El Kef, Tunisia. We report an ~1 per mil decrease in oxygen isotopic values (~5°C warming) beginning at the boundary and spanning ~300 centimeters of section (~100,000 years). The pattern found matches expectations for impact-initiated greenhouse warming.

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