Monday, 27 August 2007
1.PS-6
Analysis of the dinoflagellate cyst genus Impletosphaeridium as a marker of sea-ice conditions off Seymour Island: an ecomorphological approach
Sophie Warny, Museum of Natural Science, Louisiana State University, 119 Foster Hall, Baton Rouge, LA 70803, John B. Anderson, Earth Science, Rice University, 203 G Geology Building, 6100 Main Street, Houston, TX 77005, Laurent Londeix, Geologie et Oceanographie, Universite de Bordeaux 1, avenue des facultes, Talence Cedex, 33405, France, and Philip J. Bart, Geology and Geophysics, Louisiana State University, E235 Howe Russell Building, Baton Rouge, LA 70803.
A reworked palynological assemblage composed in majority of one genus, Impletosphaeridium spp., was found during the study of sixteen samples recovered from piston cores taken off Seymour Island, Antarctica. One of the common species, Impletosphaeridium lorum, was previously found in Seymour Island’s La Meseta Formation. Based on this similitude, we postulate that the abundance in Impletosphaeridium is linked to a late Eocene species migration. To understand the ecological significance of this event, we used an ecomorphological approach by analyzing environmental sea-surface parameters of habitats in which similar morphological extant species live. We found a high correlation between these species and sea-ice cover. If this approach is correct, and if the event is indeed Eocene, this means that the abundance in Impletosphaeridium spp. could be the first dinoflagellate event marking an extreme cooling and the onset of ephemeral ice sheet development off Seymour Island at the end of the Eocene.