GLACIALLY CONTROLLED FORAMINIFERAL DISTRIBUTIONS WITHIN THE FORMER LARSEN ICE SHELF-A AND PRINCE GUSTAV CHANNEL, ANTARCTICA

Surface sediment samples were collected from the former Larsen Ice Shelf-A (LIS-A) and the Prince Gustav Channel (PGC), eastern Antarctic Peninsula. Modern benthic and planktic foraminiferal distributions were analyzed for associations with specific environmental conditions. Cluster analyses were used to determine species distribution in these areas. Distinct trends in formaniferal assemblages are noted from the Larsen Ice Shelf-B (LIS-B) edge northward to the PGC. Four distinct assemblages were defined.

Many of the agglutinated species form an underlying assemblage that is present, with some variation throughout the LIS-A and PGC. Adercotryma glomeratum, Reophax spp., Portatrochammina spp., Textularia wiesneri, and T. antarctica constitute this baseline. The Greenpeace Trough and its periphery comprise an assemblage defined by abundant Nonionella spp., Globocassidulina biora, and Epistominella exigua. An assemblage defined by Trifarina spp. and an abundance of planktic foraminifers, including Neogloboquadrina pachyderma, is closely associated with the northern margin of the LIS-B. These two assemblages overlap near the southern boundary of the Greenpeace Trough. The northern extent of the former LIS-A region is defined by a primarily agglutinated assemblage containing a lower diversity of calcareous species than other LIS-A regions. Portatrochammina spp., Textularia wiesneri, and Epistominella exigua are prevalent in this assemblage. The PGC assemblage is defined by agglutinated foraminifers that include Textularia wiesneri, Portatrochammina spp., Miliammina spp., and Reophax spp. Planktic foraminifers were sparse in the PGC samples in comparison to the LIS-A samples; however, they were more abundant in PGC influenced by outlet glaciers. Data from the PGC also support benthic species distributions controlled by glacial and bathymetric conditions.