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The Day After the New Paper



Only one, from Science (Vol. 319. no. 5860, pp. 189 -
192. DOI: 10.1126/science.1148777)

Isotopic Evidence for Glaciation During the Cretaceous
Supergreenhouse
André Bornemann, Richard D. Norris, Oliver Friedrich,
Britta Beckmann, Stefan Schouten, Jaap S. Sinninghe
Damsté, Jennifer Vogel, Peter Hofmann, Thomas Wagner 

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 18O [the
oxygen isotope, not "180" - Eike] excursions in marine
limestones suggest that glaciation events may have
punctuated this episode of extreme warmth. New 18O
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.


Eike


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