HR: 08:15h
AN: PP11C-02    [Abstracts]
TI: Late Quaternary Biosiliceous Laminated Marine Sediments From Antarctica: Seasonality During a Period of Rapid Climate Change
AU: Pike, J
EM: pikej@cardiff.ac.uk
AF: School of Earth, Ocean and Planetary Sciences, Cardiff University, Main Building, Park Place, Cardiff, CF10 3YE United Kingdom
AU: * Stickley, C E
EM: cathy@earth.cf.ac.uk
AF: School of Earth, Ocean and Planetary Sciences, Cardiff University, Main Building, Park Place, Cardiff, CF10 3YE United Kingdom
AU: Maddison, E J
EM: MaddisonEJ@Cardiff.ac.uk
AF: School of Earth, Ocean and Planetary Sciences, Cardiff University, Main Building, Park Place, Cardiff, CF10 3YE United Kingdom
AU: Leventer, A
EM: aleventer@mail.colgate.edu
AF: Geology Department, Colgate University, 13 Oak Drive, Hamilton, , NY 13346 United States
AU: Brachfeld, S
EM: brachfelds@mail.montclair.edu
AF: Department of Earth and Environmental Studies, Montclair State University, 1 Normal Avenue, Upper Montclair, NJ 07043 United States
AU: Domack, E W
EM: edomack@hamilton.edu
AF: Geology Department, Hamilton College, 198 College Hill Road, Clinton, NY 13323 United States
AU: Dunbar, R B
EM: dunbar@stanford.edu
AF: Department of Geological and Environmental Sciences, Stanford University, 325 Braun Hall, Stanford, CA 94305 United States
AU: Manley, P L
EM: manley@middlebury.edu
AF: Geology Department, Middlebury College, Middlebury, VT 05753 United States
AU: McClennen, C
EM: cmcclennen@mail.colgate.edu
AF: Geology Department, Colgate University, 13 Oak Drive, Hamilton, , NY 13346 United States
AB: The Antarctic ice sheet plays a key role in global oceanic and atmosphere systems. One of the most dynamic regions of the continent is the Antarctic Peninsula (AP) where ecological and cryospheric systems respond rapidly to climate change, such as the last deglaciation ($\sim$12-13 kyr BP). Here, deglacial laminated diatom-rich marine sediments are well known, e.g., Palmer Deep (64$\deg$S 64$\deg$W; ODP Hole 1098A) comprising a distinctive 3 m thick sequence of deglacial `couplet' laminations. The East Antarctic margin (EAM), however, has received less attention than the West Antarctic margin (WAM) in palaeoceanographic studies yet its role in deep ocean circulation and, therefore, the global ocean system is significant. Recent sediment cores recovered from EAM sites during NSF Polar Programs-funded cruise NBP0101 in February and March 2001 (e.g. Mertz Drift \{66$\deg$S 143$\deg$E\}, Svenner Channel \{69$\deg$S 77$\deg$E\} in Prydz Bay, Nielsen Basin \{67$\deg$S 66$\deg$E\} and Iceberg Alley \{67$\deg$S 63$\deg$E\}), reveal that a similar sedimentary facies was deposited along the EAM, in similar geomorphological settings to Palmer Deep, during the same timeframe. These rich sediment archives reveal clues about circum-Antarctic palaeoceanographic change during the last deglaciation, a time of both high silica flux and rapid climate change. Microfabrics and diatom assemblages from scanning electron microscope backscattered and secondary electron imagery analysis of coeval deglacial varves from Palmer Deep (WAM), Mertz-Ninnis Trough and Iceberg Alley (EAM) are presented and compared. The varves from these localities are characterised by laminae to thin beds of orange-brown diatom ooze up to $\sim$8cm thick alternating with blue-grey diatom-bearing terrigenous sediments up to $\sim$4cm thick. The orange-brown oozes are dominated by resting spores and vegetative valves of {\itHyalochaete Chaetoceros} spp., resulting from spring sedimentation associated with stratified surface waters promoting exceptionally high primary productivity. The blue-grey terrigenous sediments contain mixed open-water Antarctic diatoms resulting from summer/autumn sedimentation associated with increased terrigenous input and the annual trend to more oligotrophic conditions. The significance of these biogenic seasonal and annual cyclicities will be discussed in terms of interannual palaeoclimate oscillations. Sub-seasonality and a related deglacial trend are apparent within the spring lamine from the EAM and in the summer/autumn laminae from the WAM. This circum-Antarctic asymmetry indicates differences in the nature and timing of oceanographic and cryospheric systems operating around the Antarctic continent at this time.
DE: 4855 Plankton
DE: 4207 Arctic and Antarctic oceanography
DE: 4215 Climate and interannual variability (3309)
DE: 4267 Paleoceanography
DE: 3030 Micropaleontology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting