Closing the mid-Eocene palaeoceanography and time scale gap and testing Eocene climate hypotheses with material and data from IODP Expedition 342 (Newfoundland)
Final Report Abstract
With this project, we set out to arrive at an astronomically calibrated timescale and palaeoceanographic record for the middle Eocene. Our new astronomically tuned, high-resolution benthic, surface and thermocline stable isotope stratigraphy represent the first integrated middle Eocene reference section from a single deep-sea location. These results revise existing magnetostratigraphic ages, and show for the first time, that the s3-s6 obliquity amplitude modulation (ca. 180kyr) is present in geological records, and on an astronomical basis, is as stable as the often used 405 kyr long eccentricity cycle. Furthermore, our new middle Eocene planktic stable isotope curves provide the first evidence for detailed analysis of precession (~20kyr) and eccentricity (~100kyr) imprints in the surface planktic records. A paired surface-thermocline analysis shows high variability with periodic collapses in the gradient, indicated periodic reorganisations of the water-column structure. In addition, further analysis of benthic stable isotope series allowed conclusions to be drawn about the onset and operation of NCW during the middle Eocene. Future steps will include the full publication of our completed planktic isotope records in the context of the yet to be assembled full benthic isotope series with our collaboration partners. This will enable outstanding questions of the timing and extent of temperature and ventilation variations during the middle Eocene to be answered for the first time.
Publications
- 2017. Data report: coarse fraction record for the Eocene megasplice at IODP Sites U1406, U1408, U1409, and U1411. In Norris, R.D., Wilson, P.A, Blum, P., and the Expedition 342 Scientists, Proceedings of the Integrated Ocean Drilling Program, 342: College Station, TX (Integrated Ocean Drilling Program)
Hull, P.M., Bohaty, S.M., Cameron, A., Coxall, H.K., D’haenens, S., De Vleeschouwer, D., Elder, L.E., Friedrich, O., Kerr, K., Turner, S.K., Kordesch, W.E.C., Moriya, K., Norris, R.N., Opdyke, B.N., Penman, D.E., Pälike, H., Wilson, P.A., Sexton, P.F., Vahlenkamp, M., Wu, F., and Zachos, J.C.
(See online at https://doi.org/10.2204/iodp.proc.342.203.2017) - (2018). Towards a robust and consistent middle Eocene astronomical timescale. Earth and Planetary Science Letters 486: 94-107
Boulila, S., M. Vahlenkamp, D. De Vleeschouwer, J. Laskar, Y. Yamamoto, H. Pälike, S. K. Turner, P. F. Sexton, T. Westerhold and U. Röhl
(See online at https://doi.org/10.1016/j.epsl.2018.01.003) - 2018, Astronomically paced changes in deep-water circulation in the western North Atlantic during the middle Eocene. Earth and Planetary Science Letters 484: 329-340
Vahlenkamp, M., Niezgodzki, N., De Vleeschouwer, D., Bickert, T., Harper, D., Kirtland Turner, S., Lohmann, G., Sexton, P., Zachos, J.D., Pälike, H.
(See online at https://doi.org/10.1016/j.epsl.2017.12.016)
