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Isotopic evidence for glaciation during the cretaceous supergreenhouse

Lookup NU author(s): Dr Britta Beckmann, Professor Thomas Wagner

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Abstract

The Turonian (93.5 to 89.3 million years ago) was one of the warmest periods of the Phanerozoic eon, with tropical sea surface temperatures over 35°C. High-amplitude sea-level changes and positive δ18O excursions in marine limestones suggest that glaciation events may have punctuated this episode of extreme warmth. New δ18O data from the tropical Atlantic show synchronous shifts ∼91.2 million years ago for both the surface and deep ocean that are consistent with an approximately 200,000-year period of glaciation, with ice sheets of about half the size of the modern Antarctic ice cap. Even the prevailing supergreenhouse climate was not a barrier to the formation of large ice sheets, calling into question the common assumption that the poles were always ice-free during past periods of intense global warming.

Publication metadata

Author(s): Bornemann A, Norris RD, Friedrich O, Beckmann B, Schouten S, Damsté JSS, Vogel J, Hofmann P, Wagner T

Publication type: Article

Publication status: Published

Journal: Science

Year: 2008

Volume: 319

Issue: 5860

Pages: 189-192

ISSN (print): 0036-8075

ISSN (electronic): 1095-9203

Publisher: American Association for the Advancement of Science

URL: http://dx.doi.org/10.1126/science.1148777

DOI: 10.1126/science.1148777

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