Completing the Eocene cyclostratigraphy - new perspectives from a greenhouse world
Final Report Abstract
In our project everything revolved around the objective to complete the Eocene cyclostratigraphy. We successfully established highly accurate stratigraphic frameworks for both Atlantic and Pacific Ocean sections while investigating crucial Ocean Drilling Program (ODP) 198 and 208 sites. We carefully generated and interpreted new high-resolution geochemical and bio-magnetostratigraphic records. To maximize the expertise of the overall approach we achieved this by an international collaborative effort. Data acquisition included nondestructive XRF core scanning, bulk and benthic stable isotopes analyses, calcareous nannofossils biostratigraphy, and natural remanent magnetization (NRM) measurements toward magnetostratigraphy. We combined the new data with published records to further build a cyclostratigraphic framework based on the stable 405-kyr eccentricity cycle metronome. The implementation of the new software tool Code for Ocean Drilling Data (CODD) developed by collaborator Dr. R. Wilkens (University of Hawai’i) has been proven as being critical for dealing with a huge dataset as the one of our project. One of the most impressive features of the new tool CODD is the ability to effectively handle core images like data and was therefore essential for example for efficiently site correlation and astronomical tuning for our project. A major result of this project is the establishment of the first complete cyclostratigraphy and astronomically tuned age model for the Ypresian Stage from Atlantic records spanning 47-56 Ma. To our surprise the geological data obtained in this project seem to reflect features of what we hypothesize an effect of the chaotic diffusion of the planetary orbits occurring ~52 Ma ago. This finding most likely will be of major importance to astronomers as it provides invaluable information on the initial conditions of the solar system. It also seems that the chaotic diffusion of the planetary orbits correlates with a global reorganization of the plate-mantle system. Hence we provocatively relate the changes in the gravitational interaction of the sun and the planets to the dynamic mantle flow of the Earth triggering plate motion reorganizations ~52 Ma ago. This interpretation caught some media attention and led to an interview for a radio feature for the Deutschlandfunk (DLF) broadcast “Forschung aktuell”. The second major achievement is the compilation of an unprecedented 12 million years long, high-resolution benthic stable isotope record for ODP Site 1209 spanning 44 to 56 Ma, extending an existing record at the same site to a now altogether unique 22 million year-long record. This record provides new insights on early to middle Eocene climate dynamics: robust evidence of multiple global warming events in the early Eocene, the first clear definition of the Early Eocene Climate Optimum (EECO, 52.0 to 49.1 Ma) and the interval of global cooling after the EECO (45.5 to 49.1 Ma) are some of the exciting results. As observed in the Atlantic isotope compilation, a major shift in benthic carbon isotope data in magnetochron C23n could now also be documented in the Pacific. Remarkably the shift seems to coincide with the global reorganization of the plate-mantle system and the chaotic diffusion of the planetary orbits as already observed in the Atlantic. High amplitude isotope variations found at ODP Site 1209 could be a fingerprint of critical transitions in the Earth climate system ~52 Ma ago leading to climate instabilities. More new high-resolution benthic stable isotope data from our project from ODP Hole 702B and Site 1263 show three distinct cooling steps in the overall cooling trend after the EECO that was previously thought to be linear. The first major, relatively abrupt step in benthic d18O at 47.120 Ma is synchronous to the first appearance for seasonal offshore sea ice in the Arctic. Our new data point to a major reorganization in the global ocean circulation at this time previously unknown due to widespread hiatuses in so far recovered deep-sea records. The ultimate outcome of this project is a for the first time complete Eocene stratigraphic record for the Atlantic and Pacific, which will be the reference and basis for future paleoceanographic research. Despite the progress made a final middle to late Eocene cyclostratigraphic framework could not be accomplished within this project. We already achieved a big step forward by establishing an Atlantic stratigraphy for Chron C18n that will be soon integrated with existing Pacific records. For the late Eocene we generated a high-resolution bulk stable isotope record that will be basis for a combined and synchronized cyclostratigraphy for Atlantic and Pacific. New results from IODP Exp. 342 reveal inconsistencies that need to be addressed in more detail in our follow up project.
Publications
- (2016) Robustness of fossil fish teeth for seawater neodymium isotope reconstructions under variable redox conditions in an ancient shallow marine setting. Geochemistry, Geophysics, Geosystems
Huck, CE, van de Flierdt, T, Jiménez-Espejo, FJ, Bohaty, SM, Röhl, U and Hammond, SJ
(See online at https://doi.org/10.1002/2015GC006218) - 2016: An abyssal carbonate compensation depth overshoot in the aftermath of the Paleocene-Eocene Thermal Maximum: Nature Geoscience
Penman, D., Kirtland Turner, S., Sexton, P., Norris, R., Dickson, A., Boulila, S., Ridgwell, A., Zeebe, R., Zachos, J., Cameron, A., Westerhold, T., and Röhl, U.
(See online at https://doi.org/10.1038/NGEO2757) - 2016: Environmental perturbations at the early Eocene ETM2, H2, and I1 events as inferred by Tethyan calcareous plankton (Terche section, northeastern Italy): Paleoceanography, 31, 1225–1247
D'Onofrio, R., V. Luciani, E. Fornaciari, L. Giusberti, F. Boscolo Galazzo, E. Dallanave, T. Westerhold, M. Sprovieri, and S. Telch
(See online at https://doi.org/10.1002/2016PA002940) - 2017: Astronomical Calibration of the Ypresian Time Scale: Implications for Seafloor Spreading Rates and the Chaotic Behaviour of the Solar System?, Clim. Past Discuss., 2017, 1-34
Westerhold, T., Röhl, U., Frederichs, T., Agnini, C., Raffi, I., Zachos, J.C., and Wilkens, R. H.
(See online at https://doi.org/10.5194/cp-2017-15) - 2017: Orbital Forcing of the Paleocene and Eocene Carbon Cycle, Paleoceanography
Zeebe, R. E, Westerhold, T., Littler, K., and Zachos, J. C.
(See online at https://doi.org/10.1002/2016PA003054)
