HR: 0830h
AN: PP51B-0927    [PDF]
TI: Coccolith Carbonate Burial in the Open Ocean: Neogene Patterns
AU: * Henderiks, J
EM: jorijntje.henderiks@geo.su.se
AF: Dept. of Geology and Geochemistry, Stockholm University, Stockholm, S-106 91 Sweden
AB: Coccolithophorids, gold-brown algae, are prominent primary producers in the World's oceans. They produce calcite scales (coccoliths) that surround their cell, which represents a potential short-term CO$_{2}$ source to the environment. The burial of coccoliths into marine sediments acts as a long-term sink of carbon. In fact, sedimentary carbonates are the largest reservoir of carbon on Earth, and hence play a vital role in the global carbon cycle. The contribution by coccolithophorids to this long-term sink can be expressed by accumulation rates of fine fraction carbonate. In more detail, absolute abundances of coccoliths combined with species-specific carbonate weights can resolve which taxa are most effective contributors to deep-sea carbonate. Surprisingly little has been done to link biogenic calcium carbonate budgets in the geological past to the general evolutionary patterns of calcifying plankton. Coccolithophorids have evolved relatively rapidly since their first appearance in the Mesozoic. Their evolutionary patterns are characterized by several periods of increasing species diversity and subsequent decline, as well as changes in their coccolith size and morphology. An overall decrease in the coccolith sizes is recorded during the Neogene, with the disappearance of large coccoliths ($>$10 micron) since the Middle Miocene. Because larger coccoliths are generally more resistant to dissolution, this observation cannot be due to (selective) carbonate dissolution. Hence, it implies significant variability in the amount of coccolith carbonate effectively buried through time, and potentially drastic changes in coccolithophorid productivity in the open ocean, with consequences for the short-term effects of biocalcification. This study focuses on Neogene proportions and accumulation rates of coccolith carbonate in selected well-preserved DSDP and ODP Sites from the Atlantic, Pacific and Indian Oceans, at a 1-2 M.y. resolution. Ultimately, the aim is to understand the observed variability in the context of global climate change, ocean chemistry fluctuations and plankton evolution during the Neogene.
DE: 4267 Paleoceanography
DE: 4806 Carbon cycling
DE: 4855 Plankton
DE: 9604 Cenozoic
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting