HR: 0800h
AN: PP41B-0649    [Abstracts]
TI: Warm Interglacial MIS 31 in the Subpolar South Atlantic: Evidence from ODP Site 177-1090.
AU: * Teitler, L
EM: Lora.Teitler@csueastbay.edu
AF: California State University, East Bay, 25800 Carlos Bee Blvd., Hayward, CA 94542 United States
AU: Warnke, D A
EM: Dietz.Warnke@csueastbay.edu
AF: California State University, East Bay, 25800 Carlos Bee Blvd., Hayward, CA 94542 United States
AU: Venz, K
EM: venz@ufl.edu
AF: University of Florida, 241 Williamson Hall, Gainesville, FL 32611 United States
AU: Hodell, D A
EM: dhodell@geology.ufl.edu
AF: University of Florida, 241 Williamson Hall, Gainesville, FL 32611 United States
AB: We recently completed a study of ice-rafted debris (IRD) contained in samples from deep-sea cores (ODP Leg 177, Site 1090) from the subpolar South Atlantic Ocean, that covered the time span from mid-MIS 34 to the beginning of MIS 30 (about 1.055 to 1.120 ma). The IRD Index ((IRD/[IRD+planktic forams]) X 100) is highest mid-MIS 34, dropping immediately to a low but persistent rate which continues throughout stages 33-31, only rising again as MIS 30 develops. The low rate is comparable to those seen during MIS 11 and 5e at the same location. Background rafting (the presence of IRD in a sample but outside of the counted split) is also present in many samples. A dropstone a little more than 2 mm in diameter, identifiable as quartz diorite, arrived during MIS 33 during a strong stadial. Garnets are present in many of these samples, as they are from MIS 14 to the present in samples from the same location. We have previously suggested that the presence of garnets at this remote site must be an indication of transport by icebergs from East Antarctica, where garnets are found in many locations. Garnets have been noted by various investigators in the marine sediments around Antarctica; Diekmann and Kuhn (1999, Marine Geology, v 158, p 209-231) cited the presence of garnets in proximal sediments as evidence for an East Antarctic origin. Major stadials are visible in the benthic foraminifer oxygen isotopic records during both MIS 33 and 31, with corresponding increases in the IRD Index. The radiolarian Dictyocoryne profunda Ehrenberg ( sensu Boltovskoy, 1998, http://palaeo-electronica.org/1998_2/boltovskoy/issue2.htm; [i.e.= Hymeniastrum euclidis ]), a possible warm temperature indicator, is also present, usually in the warmer sections, most commonly during MIS 31. Notably, they are absent during MIS 33, a relatively cold interglacial with a particularly strong stadial. We conclude that during this time interval, large continental glaciers continued to reach the ocean from East Antarctica, launching icebergs capable of reaching this distal location. We have no evidence, however, concerning the presence or absence of the West Antarctic Ice Sheet (WAIS) through this time. If it can be proven that the WAIS did collapse, then it must be concluded that the absence of the WAIS has no major effect on the Weddell Sea Gyre or the path of East Antarctic icebergs into the South Atlantic.
DE: 0732 Icebergs
DE: 3036 Ocean drilling
DE: 4940 Isotopic stage
SC: Paleoceanography and Paleoclimatology [PP]
MN: Fall Meeting 2005