The Campanian - Maastrichtian (Late Cretaceous) climate transition: the history of palaeoceanographic changes
Zusammenfassung der Projektergebnisse
During this project, a new high-resolution δ13C record was generated for the latest Cretaceous tropical Pacific in order to improve the stratigraphic resolution. Together with new δ13C data from Gubbio, Italy, it resolves short-lived isotopic events between 75-66 Ma suitable for global correlation. The global correlation allows the identification of significant high-frequency δ13C variations that occur superimposed on prominent Campanian–Maastrichtian events, namely the Late Campanian Event (LCE), the Campanian–Maastrichtian Boundary Event (CMBE), the mid-Maastrichtian Event (MME), and the Cretaceous-Paleogene transition (KPgE). The Gubbio section has a detailed magnetostratigraphy and serves as subtropical reference for the biozonation with calcareous nannofossils and planktonic foraminifera. The features of the δ13C record at Hole 1210B thus can be calibrated to paleomagnetic reversals and the current time scale. To reliably reconstruct the mode of Cretaceous deep-ocean circulation, a thorough mapping of intermediate- to deep-water masses and their mixing covering all ocean basins is essential. The generation of high-resolution Nd-isotope records, obtained from ferromanganese-oxide coatings from three Campanian-Maastrichtian sites in the South Atlantic (DSDP Site 525, Walvis Ridge), the Southern (ODP Site 690, Maud Rise), and the proto-Indian (ODP Site 762, Exmouth Plateau) oceans are thus an important main result of this project. Comparison of these new with published Nd isotope data shows the presence of significantly different neodymium-isotope signatures at intermediate depths, which provides evidence for local intermediate water sources in the South Atlantic and Southern oceans. In particular, an intermediate water mass with a highly radiogenic neodymium-isotope signature bathed the top of the Walvis Ridge, a structure that formed a barrier between the Southern Ocean and the North Atlantic oceanic basins. Our new results suggest that deep-water exchange between the Atlantic and other oceans was restricted until the late Maastrichtian. This has fundamentally implications for the mode of ocean circulation in a small ocean basin, which was different from today and was possibly driven by mesoscale eddies. The tectonically induced deepening of ocean basins by mid-ocean ridge subduction and gateway opening played an important role in the global linkage of oceanic deep-water and carbon reservoirs and the establishment of a global thermohaline circulation system. Deep-sea temperature reconstructions in the tropical Pacific (Site 1210) demonstrate a three million year long period (72.5 to 69.5 Ma) of cooler conditions, which coincided with a concomitant change in seawater Nd isotope signatures toward less radiogenic values over a broad range of bathyal to abyssal water depths (Jung et al., submitted). This cool period commenced at the beginning of the CMBE and is interpreted to be the result of enhanced northward flow and admixture of deep waters with a Southern Ocean provenance (SCW). This change possibly resulted from enhanced deep-water formation in the Southern Ocean, increased deep convection, and overall intensification of ocean circulation in the Pacific. The close relation of the early Maastrichtian cold interval to the CMBE together with its long duration on million-year timescales argues for tectonic forcing. Tectonic processes were responsible for changes in oceanic bathymetry, and/or in the exchange of deep waters between oceanic basins, and thus may have influenced deep oceanic convection and the intensity of ocean circulation in the Pacific Ocean.
Projektbezogene Publikationen (Auswahl)
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2010. Campanian – Maastrichtian carbon isotope stratigraphy: shelf–ocean correlation between the European shelf sea and the tropical Pacific Ocean. Newsletters on Stratigraphy 44/1, 57-72
Voigt, S., Friedrich, O., Norris, R .D., Schönfeld, J.
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High-resolution stable isotope stratigraphy across the Campanian – Maastrichtian boundary at Shatsky Rise. – 10th International Conference on Paleoceanography, Aug 29 – Sep 3 2010, San Diego, abstract
Jung, C., Voigt, S., Friedrich, O., Frank, M., Gale, A.S., Jenkyns, H.
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2012. High-resolution carbon-isotope stratigraphy across the Campanian-Maastrichtian boundary at Shatsky Rise (tropical Pacific). Cretaceous Research, 37, 177-187
Jung, C., Voigt, S., Friedrich, O.
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2012. Late Campanian to Maastrichtian palaeoceanographic changes in the tropical Pacific. – Geophysical Research Abstracts 14, EGU2012-7408
Jung, C., Voigt, S., Friedrich, O., Frank, M.
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Tectonically induced multiple intermediate and deep-water sources in the Cretaceous ocean. - GV & Sediment Meeting, Hamburg, September 23-28, 2012, Abstract Volume, p. 132
Jung, C., Hoffmann, J., Friedrich, O., Frank, M., Voigt, S.
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2013. Tectonically restricted deep-ocean circulation at the end of the Cretaceous greenhouse. Earth and Planetary Science Letters, 369-370, 169-177
Voigt, S., Jung, C., Friedrich, O., Frank, M., Teschner, C., Hoffmann, C.
