HR: 16:15h
AN: PP14A-02    [Abstracts]
TI: Multiple Early Eocene Thermal Maximums
AU: * Roehl, U
EM: uroehl@marum.de
AF: DFG Research Center for Ocean Margins (RCOM), Department of Geosciences, Bremen University, Postfach 33 04 40, Klagenfurter Strasse, Bremen, 28334 Germany
AU: Zachos, J C
EM: jzachos@emerald.ucsc.edu
AF: Earth Sciences Department, University of California Santa Cruz (UCSC), Earth and Marine Sciences Building, Santa Cruz, CA 95064 United States
AU: Thomas, E
EM: ethomas@wesleyan.edu
AF: Wesleyan University, 265 Church Street, Middletown, CT 06459-0139 United States
AU: Kelly, D C
EM: ckelly@geology.wisc.edu
AF: Department of Geology and Geophysics, University of Wisconsin-Madison, 1215 West Dayton Street, Madison, WI 53706 United States
AU: Donner, B
EM: donner@uni-bremen.de
AF: DFG Research Center for Ocean Margins (RCOM), Department of Geosciences, Bremen University, Postfach 33 04 40, Klagenfurter Strasse, Bremen, 28334 Germany
AU: Westerhold, T
EM: tho@uni-bremen.de
AF: DFG Research Center for Ocean Margins (RCOM), Department of Geosciences, Bremen University, Postfach 33 04 40, Klagenfurter Strasse, Bremen, 28334 Germany
AB: Periodic dissolution horizons signifying abrupt shoaling of the lysocline and CCD are characteristic features of deep-sea sections and often attributed to Milankovitch forcing via their diagnostic frequencies. Prominent dissolution horizons also correspond to abrupt climate events, such as the Paleocene-Eocene thermal maximum (PETM), as a result of input of significant CH$_{4}$ - CO$_{2}$ into the ocean-atmosphere system. The question arises whether other significant dissolution horizons identified in sediments of late Paleocene and early Eocene age similar to the recently identified ELMO (Lourens et al., 2004) were formed as a result of greenhouse gas input, or whether they were related to cumulative effects of periodic changes in ocean chemistry and circulation. Here we report the discovery of a 3$^{rd}$ thermal maximum in early Eocene (about 52 Ma) sediments recovered from the South Atlantic during ODP Leg 208. The prominent clay layer was named the "X" event and was identified within planktonic foraminifer zone P7 and calcareous nannofossil zone CP10 at four Walvis Ridge Transect sites with a water depth range of 2000 m (Sites 1262 to 1267). Benthics assemblages are composed of small individuals, have low diversity and high dominance. Dominant taxa are {\it Nuttallides truempyi} and various abyssaminids, resembling the post PETM extinction assemblages. High-resolution bulk carbonate \delta$^{13}$C measurements of one of the more shallow Sites 1265 reveal a rapid about 0.6 per mill drop in \delta$^{13}$C and \delta$^{18}$O followed by an exponential recovery to pre-excursion \delta$^{13}$C values well known for the PETM and also observed for the ELMO. The planktonic foraminiferal \delta$^{13}$C records of {\it Morozovella subbotina} and {\it Acaranina soldadoensis} in the deepest Site 1262 show a 0.8 to 0.9 per mill drop, whereas the \delta$^{13}$C drop of benthic foraminifera {\it Nuttallides truempyi} is slightly larger (about 1 per mill). We are evaluating mechanisms for the widespread change in deep-water chemistry, its connection to the surface-water response, and the relationship of the event, as well as the PETM and ELMO, with current astronomical solutions (Laskar et al., 2004; Varadi et al., 2003). References 1. Lourens, L.J., Sluijs, A., Kroon, D., Zachos, J.C., Thomas, E., Roehl, U., and the ODP Leg 208 Shipboard Scientific Party, 2004. An early Eocene transient warming (~53 Ma): Implications for astronomically-paced early Eocene hyperthermal events.- Abstract, 8th International Conference on Paleoceanography (ICP), 5-10 September 2004, Biarritz, France. 2. F. Varadi, B. Bunnegar, M. Ghil, Astrophysical J. 592, 620-630 (2003). 3. J. Laskar et al., Astronomy and Astrophysics (2004).
DE: 9325 Atlantic Ocean
DE: 4267 Paleoceanography
DE: 3030 Micropaleontology
DE: 1050 Marine geochemistry (4835, 4850)
DE: 1620 Climate dynamics (3309)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting