HR: 10:20h
AN: PP42A-01 INVITED     [Abstracts]
TI: Long-Term Trends in the Global Carbon Cycle: Biogeochemical Records of the Past 205 myrs
AU: * Katz, M E
EM: mimikatz@rci.rutgers.edu
AF: Dept. Geological Sci. 610 Taylor Rd., Rutgers Univ., Piscataway, NJ 08854 United States
AU: Fennel, K
EM: kfennel@imcs.rutgers.edu
AF: Dept. Geological Sci. 610 Taylor Rd., Rutgers Univ., Piscataway, NJ 08854 United States
AU: Fennel, K
EM: kfennel@imcs.rutgers.edu
AF: Inst. of Marine & Coastal Sci. 71 Dudley Rd., Rutgers Univ., New Brunswick, NJ 08901 United States
AU: Berner, R A
EM: robert.berner@yale.edu
AF: Dept. of Geology and Geophysics, Yale Univ., New Haven, CT 06520 United States
AU: Falkowski, P G
EM: falko@imcs.rutgers.edu
AF: Dept. Geological Sci. 610 Taylor Rd., Rutgers Univ., Piscataway, NJ 08854 United States
AU: Falkowski, P G
EM: falko@imcs.rutgers.edu
AF: Inst. of Marine & Coastal Sci. 71 Dudley Rd., Rutgers Univ., New Brunswick, NJ 08901 United States
AB: Atmospheric and seawater chemistry are modified through time by both geological and biological processes: tectonic outgassing in combination with erosional processes are the primary suppliers of most major elements in geochemical cycles; biologically-mediated redox processes alter mobile elemental reservoirs before geologic processes sequester (remove) elements from these mobile reservoirs. We present Jurassic-Cenozoic carbon isotope records for carbonates and organic matter generated from bulk sediment samples from the Atlantic (sample resolution of 200 kyrs), and infer from these records changes in redox conditions and biological processes that affected atmospheric and seawater chemistry through time. We use our carbon isotope records with published sulfur isotopes of sulfates in model simulations to reconstruct carbon burial, pCO2 and pO2 over the past 205 myrs; our model results indicate that organic C burial and pO2 have increased, while pCO2 has decreased. The evolution and expansion of the larger-celled eucaryotic phytoplankton of the red-plastid lineage, coupled with the opening of the Atlantic Ocean basin and global sea-level rise, led to this increase in organic carbon burial beginning in the Early Jurassic as the supercontinent Pangea broke apart. This organic C burial increased the oxidation state of Earth's surface reservoirs while drawing down atmospheric CO2, which in turn acted as a strong selective agent in both marine and terrestrial primary producers, resulting in the rise in C4 and beta-carboxylation photosynthetic pathways in the latter part of the Cenozoic. At the same time, O2 levels approximately doubled, with relatively fast increases in the Early Jurassic and the Eocene. The rise of oxygen may have been a key factor in the evolution, radiation, and subsequent increase in the average size of placental mammals during the Cenozoic.
DE: 0428 Carbon cycling (4806)
DE: 3036 Ocean drilling
DE: 4855 Phytoplankton
DE: 4870 Stable isotopes (0454, 1041)
DE: 4912 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 1615, 4805)
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005