LATE CRETACEOUS OCEANS AND THE COOL TROPIC PARADOX

Oxygen isotopic proxies of paleo-sea surface temperatures (SSTs) sugge st that Maastrichtian (about 66 million years ago) tropical SSTs were lower than those of today, They also demonstrate that Maastrichtian la titudinal SST gradients were much lower than those of the present. The low Maastrichtian SST gradients indicate that meridional heat transpo rt was much greater or latitudinal differences in the balance of radia tion to and from the sea surface were much less extreme during the lat est Cretaceous than they are today, or that both conditions were true, These findings challenge traditional interpretations of ''greenhouse' ' Late Cretaceous climates.