Isotopic Evidence for Glaciation During the Cretaceous Supergreenhouse

• Published in: Science
• Main Authors: Bornemann, André, Norris, Richard D., Friedrich, Oliver, Beckmann, Britta, Schouten, Stefan, Damsté, Jaap S. Sinninghe, Vogel, Jennifer, Hofmann, Peter, Wagner, Thomas
• Format: Article in Journal/Newspaper
• Language: English
• Published: American Association for the Advancement of Science (AAAS) 2008
• Subjects: Antarctic; Antarc*; Ice cap
• Online Access: http://dx.doi.org/10.1126/science.1148777; https://www.science.org/doi/pdf/10.1126/science.1148777

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 δ 18 O excursions in marine limestones suggest that glaciation events may have punctuated this episode of extreme warmth. New δ 18 O 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.