HR: 11:35h
AN: PP42A-06    [Abstracts]
TI: Carbonate Lysocline and d13C Changes at the PETM:
How Much Carbon?
AU: * Ridgwell, A
EM: andy@seao2.org
AF: University of British Columbia, Department of Earth and Ocean Sciences University of British Columbia, Vancouver, BC V6T1Z4 Canada
AU: Panchuk, K
EM: kpanchuk@geosc.psu.edu
AF: Penn State, Dept. of Geosciences Penn State 535 Deike Bldg., University Park, PA 16802 United States
AU: Kump, L
EM: lkump@psu.edu
AF: Penn State, Dept. of Geosciences Penn State 535 Deike Bldg., University Park, PA 16802 United States
AB: Prominent δ¹³C excursions in the geologic record are often interpreted as a transfer of isotopically depleted carbon into or out of the ocean and atmosphere. However, because different sources and sinks of this carbon have different isotopic characteristics, a second observed variable is required in order to unambiguously determine the total amount of carbon involved. For instance, during the deglacial transitions of the late Neogene, the observed benthic δ¹³C increase that is traditionally interpreted as a ca. 500 GtC removal to the terrestrial biosphere may also be influenced by the input of methane hydrate carbon, thus allowing for a considerably greater biosphere expansion.
For the catastrophic carbon release inferred for the Paleocene-Eocene Thermal Maximum (PETM), the observed 2-3 per mil benthic δ¹³C decrease was originally explained by a ~2000 GtC release of -60 per mil CH₄. However, the very pronounced shoaling of the carbonate lysocline observed during the event has been interpreted as evidence for a much larger input of carbon. A larger carbon input, in turn, points to a less depleted carbon source, such as terrestrial biomass (~-23 per mil).
Here we outline a new interpretation of the observed PETM lysocline changes based on evidence for the development of anoxic or dysoxic conditions, particularly in the Altantic basin, and the impact that this has on the dissolution of previously sedimented carbonates. Sensitivity analysis using an Earth system model confirms that if our interpretation is right, then a smaller carbon input than was previously assumed is required in order to explain the observed lysocline response.
UR: http://mygenie.seao2.org
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
DE: 4924 Geochemical tracers
DE: 4928 Global climate models (1626, 3337)
DE: 4948 Paleocene/Eocene thermal maximum
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005