HR: 0800h
AN: PP11B-0570    [Abstracts]
TI: Evolutionary Events and Phytoplankton Recovery After the K/T Mass Extinction
AU: * Fuqua, L M
EM: lfuqua@geosc.psu.edu
AF: The Pennsylvania State University, Deike Building, University Park, PA 16802 United States
AU: Bralower, T J
EM: bralower@geosc.psu.edu
AF: The Pennsylvania State University, Deike Building, University Park, PA 16802 United States
AB: The recovery of the open ocean ecosystem after the Cretaceous-Tertiary boundary mass extinction (65 Ma) was extremely slow. The surface to deep carbon isotopic gradient remained below latest Cretaceous levels for more than three million years after the boundary event, suggesting suppressed rates of carbon cycling and low phytoplankton productivity. There is a rapid change in the carbon isotopic gradient between 62 and 61 Ma, indicating the final recovery of surface water production levels (D'Hondt et al., 1998). We are investigating nannoplankton communities in the interval from 61.5 to 62.5 Ma to determine the relationship between the recovery and changes in productivity and carbon cycling. Samples were collected at high resolution from Ocean Drilling Program Site 1209 in the western Pacific, and Deep Sea Drilling Project Sites 384 in the North Atlantic and 528 in the South Atlantic. Results show major diversification of two dominant Cenozoic nannoliths (non-coocolith bearing, calcite-secreting nannoplankton), {\it Fasciculithus} and {\it Sphenolithus}, occurred shortly after carbon gradients were restored. The first occurrences of these two genera are associated with significant changes in calcareous nannoplankton communities, indicative of abrupt changes in surface water circulation. A rapid evolutionary sequence of early forms of {\it Fasciculithus} has been identified at Sites 1209 and 384. Two unidentified taxa were found before the first occurrence of the earliest documented species, {\it F. pileatus}. SEM work currently underway is designed to elucidate the evolution of this genus. At the Pacific site, the diversification is associated with an interval of dissolution, presumably resulting from a change in deep water circulation. The significance of this relationship is currently not understood. D'Hondt, S. et al., Organic carbon fluxes and ecological recovery from the Cretaceous-Tertiary mass extinction, Science, 282, 276-279, 1998.
DE: 4267 Paleoceanography
DE: 4532 General circulation
DE: 3030 Micropaleontology
DE: 1635 Oceans (4203)
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting