Articles | Volume 12, issue 2
Research article
24 Feb 2016
Research article |  | 24 Feb 2016

Late Cretaceous (late Campanian–Maastrichtian) sea-surface temperature record of the Boreal Chalk Sea

Nicolas Thibault, Rikke Harlou, Niels H. Schovsbo, Lars Stemmerik, and Finn Surlyk

Abstract. The last 8 Myr of the Cretaceous greenhouse interval were characterized by a progressive global cooling with superimposed cool/warm fluctuations. The mechanisms responsible for these climatic fluctuations remain a source of debate that can only be resolved through multi-disciplinary studies and better time constraints. For the first time, we present a record of very high-resolution (ca. 4.5 kyr) sea-surface temperature (SST) changes from the Boreal epicontinental Chalk Sea (Stevns-1 core, Denmark), tied to an astronomical timescale of the late Campanian–Maastrichtian (74 to 66 Ma). Well-preserved bulk stable isotope trends and calcareous nannofossil palaeoecological patterns from the fully cored Stevns-1 borehole show marked changes in SSTs. These variations correlate with deep-water records of climate change from the tropical South Atlantic and Pacific oceans but differ greatly from the climate variations of the North Atlantic. We demonstrate that the onset and end of the early Maastrichtian cooling and of the large negative Campanian–Maastrichtian boundary carbon isotope excursion are coincident in the Chalk Sea. The direct link between SSTs and δ13C variations in the Chalk Sea reassesses long-term glacio-eustasy as the potential driver of carbon isotope and climatic variations in the Maastrichtian.

Short summary
We present here for the first time a very high-resolution record of sea-surface temperature changes in the Boreal Chalk Sea for the last 8 million years of the Cretaceous. This record was obtained from 1932 bulk oxygen isotope measurements, and their interpretation into temperature trends is validated by similar trends observed from changes in phytoplankton assemblages.