A new high resolution stable isotope record from the North Atlantic Ocean: a detailed insight into the mid-Maastrichtian event

Abstract

The long-term global cooling trend during the latest Cretaceous was interrupted by an intense global warming episode at ~69 Ma known as the mid-Maastrichtian event (MME). The MME is characterized by two positive 13C excursions with an overall magnitude of 0.6‰ to 1.5‰ separated by a negative inflection. The 13C excursions are accompanied by the extinction of inoceramid bivalves, an abrupt increase in deep-sea and sea-surface temperatures as well as terrestrial mean annual temperatures between 21 and 23 °C at a paleolatitude of ~35° N. Changes in oceanic circulation, particularly a change in thermohaline circulation patterns, have been identified to be one of the main drivers of the MME. Nevertheless, the driving mechanisms, timing, character, and consequences of the circulation change are still up for debate. In this study, a 2 Myr-long time interval of the Mid to Late Maastrichtian has been analyzed at a ~2.5 to 5 kyr-resolution with the aim to improve the understanding of the climatic patterns leading to the MME. For IODP Core U1403 in the North Atlantic (J-Anomaly Ridge), XRF core scanning, wt% CaCO3 analyses, and stable oxygen and carbon isotope records of benthic foraminifera were generated. Bottom-water temperatures were reconstructed through Mg/Ca measurements of the same foraminiferal tests. Preliminary data reveal a warming of North Atlantic deep-sea temperatures by ~2–3°C between ~68.5 and 69 Ma, accompanied by several CaCO3 dissolution events as well as 13C excursions of up to 0.8 ‰. These findings point towards a major perturbation in the global carbon cycle accompanying the overall change in ocean circulation whose causes appear to be more complex than previously thought.