Earth's climate during the Maastrichtian (latest Cretaceous) was punctuated by brief warming and cooling episodes, accompanied by perturbations of the global carbon cycle. Superimposed on a long-term cooling trend, the middle Maastrichtian is characterized by deep-sea warming and relatively high values of stable carbon-isotope ratios, followed by strong climatic variability towards the end of the Cretaceous. A lack of knowledge on the timing of climatic change inhibits our understanding of underlying causal mechanisms. We present an integrated stratigraphy from Integrated Ocean Drilling Program (IODP) Site U1403, providing an expanded deep ocean record from the North Atlantic (Expedition 342, Newfoundland Margin). Distinct sedimentary cyclicity suggests that orbital forcing played a major role in depositional processes, which is confirmed by statistical analyses of high resolution elemental data obtained by X-ray fluorescence (XRF) core scanning. Astronomical calibration reveals that the investigated interval encompasses seven 405-kyr cycles (Ma4051 to Ma4057) and spans the 2.8 Myr directly preceding the Cretaceous/Paleocene (K/Pg) boundary. A high-resolution carbon-isotope record from bulk carbonates allows us to identify global trends in the late Maastrichtian carbon cycle. Low-amplitude variations (up to 0.4‰) in carbon isotopes at Site U1403 match similar scale variability in records from Tethyan and Pacific open-ocean sites. Comparison between Site U1403 and the hemipelagic restricted basin of the Zumaia section (northern Spain), with its own well-established independent cyclostratigraphic framework, is more complex. Whereas the pre-K/Pg oscillations and the negative values of the Mid-Maastrichtian Event (MME) can be readily discerned in both the Zumaia and U1403 records, patterns diverge during a ~ 1 Myr period in the late Maastrichtian (67.8-66.8 Ma), with Site U1403 more reliably reflecting global carbon cycling. Our new carbon isotope record and cyclostratigraphy offer promise for Site U1403 to serve as a future reference section for high-resolution studies of late Maastrichtian paleoclimatic change.
Bibliographical noteFunding Information:
This research used samples provided by the Integrated Ocean Drilling Program (IODP), which is sponsored by the U.S. National Science Foundation and participating countries under management of Joint Oceanographic Institutions, Inc. This research used data acquired at the XRF Core Scanner Lab at the MARUM-Center for Marine Environmental Sciences, University of Bremen, Germany. Sven Hofmann is thanked for laboratory assistance. Dominik Leonhardt helped with processing of sediment samples. We would like to thank Nicolas Thibault, Helmut Weissert, and two anonymous reviewers for comments on an earlier version of the manuscript. Funding for this study was provided by the DFG to O. F. (Emmy Noether research group 'Meso-and Cenozoic paleoceanography'; grant FR2544/2-1 and grant FR2544/5) and to S.V. (DFG grant VO 687/14-1). The bulk carbon isotope and oxygen isotope data, as well as the Si, Ca, Fe and Ba counts from XRF analyses, are available in the Pangaea database (doi. pangaea.de/10.1594/PANGAEA.875743).
© 2017 Gebrüder Borntraeger, Stuttgart, Germany.
- Astronomical climate forcing
- Carbon isotopes
- Integrated stratigraphy
- Ocean Drilling Program Site U1403 (Newfoundland)