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Paper No. 50-10
Presentation Time: 1:30 PM-5:30 PM
STABLE ISOTOPES RECORD PALEOCLIMATIC CHANGES ACROSS THE LATEST MAASTRICHTIAN CHALK GROUP, NORTHERN JUTLAND, DENMARK
During the Late Cretaceous Period, Earth experienced substantial cooling after a thermal maximum during the Turonian Stage. Superimposed on this long-term trend are short-term climatic fluctuations during the Maastrichtian Stage, which occurred as a response to emplacement of the Deccan Trap large igneous province. At the end of the Maastrichtian Stage, greenhouse warming during Phase 2 of Deccan volcanism was followed by a global cooling trend in the 100-150 kyr before the Cretaceous-Paleogene (K-Pg) boundary. Evidence for these events is apparent in isotopic data and calcareous nannofossil assemblages from sites worldwide. In the Danish Basin, this climate transition is potentially represented by a distinct facies change from white chalk mudstone of the Sigerslev Member to grey chalk wackestone with abundant skeletal fragments in the Højerup Member of the Chalk Group. However, no stable isotope data have thus far pinpointed these climatic shifts in the famous section of Stevns Klint, nor anywhere else in the Danish Basin. This study examines carbon and oxygen isotope data from chalk samples collected from a new section near Hundstrup, northern Jutland, Denmark. This section covers ~8.5 meters of strata before the K-Pg boundary—which is thought to represent 200-250 kyr of deposition—as well as the K-Pg boundary and the first ~1 meter of overlying Danian strata. Our results demonstrate a clear positive shift in oxygen isotope compositions of roughly 1 ‰ from the Sigerslev-Højerup facies transition up to the K-Pg boundary. We interpret these data as evidence for a decline in sea surface temperatures in the Danish Basin over the last 100-150 kyr of the Cretaceous Period, associated with the waning of Deccan Trap volcanism. Future work is aimed at correlating our results to the nearby Nye Kløv section that spans the same interval, and corroborating these findings using nannofossil assemblages in these two sections.