Evidence for global cooling in the Late Cretaceous

The Late Cretaceous 'greenhouse' world witnessed a transition from one of the warmest climates of the past 140 million years to cooler conditions, yet still without significant continental ice. Low-latitude sea surface temperature (SST) records are a vital piece of evidence required to unravel the cause of Late Cretaceous cooling, but high-quality data remain illusive. Here, using an organic geochemical palaeothermometer (TEX86), we present a record of SSTs for the Campanian-Maastrichtian interval (similar to 83-66 Ma) from hemipelagic sediments deposited on the western North Atlantic shelf. Our record reveals that the North Atlantic at 35 degrees N was relatively warm in the earliest Campanian, with maximum SSTs of similar to 35 degrees C, but experienced significant cooling (similar to 7 degrees C) after this to <similar to 28 degrees C during the Maastrichtian. The overall stratigraphic trend is remarkably similar to records of high-latitude SSTs and bottom-water temperatures, suggesting that the cooling pattern was global rather than regional and, therefore, driven predominantly by declining atmospheric pCO(2) levels.