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

Abstract

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.

The impact of the Maastrichtian cooling on the marine nutrient regime—Evidence from midlatitudinal calcareous nannofossils

“…Below marly layer mB615/616 (~17 m), this species is a common component of the assemblage contributing about 8.4% to the entire abundance pattern, whereas it is rare above (~1.5%; Figure b). A decline on the same magnitude has been reported from the southern high latitudes [e.g., Watkins et al ., ] and in quantitative nannofossil studies from Denmark [ Thibault et al ., , ]. Further evidence for an early Maastrichtian abundance decline of W .…”

“…barnesiae was most abundant in near equatorial settings (>30%), whereas it was absent in high latitudes [ Thierstein , ; Watkins et al ., ]. The observed decline was probably the consequence of an earliest Maastrichtian climate cooling [e.g., Li and Keller , , ; Barrera and Savin , ; Linnert et al ., ; Thibault et al ., , ].…”

“…A similar increase of W . barnesiae is also seen in Denmark [ Thibault et al ., ] indicating a short paleoenvironmental perturbation affecting the entire North Sea Basin. This perturbation is evidenced by a simultaneous pulse of Micula (Figure b), a genus, which was previously assigned to stressful conditions [e.g., Thibault and Gardin , , ].…”

“…It is unlikely that warming initiated this pulse of W . barnesiae , because neither the oxygen isotope data from Kronsmoor [ Friedrich et al ., ; Voigt et al ., , ] nor those from Denmark [ Thibault et al ., , ] indicate a short warm snap, which might have interrupted the general cooling. The sudden, short term abundance increase of W .…”

“…For midlatitudinal settings there is only one study available, which demonstrates a considerable response of calcareous nannofossils to the Campanian‐Maastrichtian cooling [ Thibault et al ., ]. This study is, however, focused on a few proxy taxa ( W .…”