SOUTHERN OCEAN VENTILATION AND PRODUCTIVITY ACROSS THE LAST DEGLACIATION

• Main Author: LE MEUR, GERALDINE
• Other Authors: Faculty of Science
• Format: Thesis
• Language: English
• Published: 2004
• Subjects: palaeoceanography; benthic foraminifera; productivity; ventilation; Southern Ocean; Kerguelen plateau; Kerguelen; Indian
• Online Access: http://hdl.handle.net/10026.2/1918

The Southern Ocean is identified as one of the main oceanographic structure of the global ocean and is therefore a key area for understanding changes in oceanographic and environmental conditions. In this paper, we present results of micropalaeontological analysis and stable isotopic records of one deep-sea core MD02-2488 collected in the Southern Ocean , South-eastern Indian sector (46°28.8'S, 88°01.3'E, 3420 m water depth) The core stratigraphy, obtained from oxygen isotopic composition of planktonic and benthic foraminifera, indicates a continuous and undisturbed sedimentary record from the end of the last glacial period to present. Benthic foraminiferal study, using Principal Component Analysis, and The Southern Ocean is identified as one of the main oceanographic structure of the global ocean and is therefore a key area for understanding changes in oceanographic and environmental conditions. In this paper, we present results of micropalaeontological analysis and stable isotopic records of one deep-sea core MD02-2488 collected in the Southern Ocean , South-eastern Indian sector (46°28.8'S, 88°01.3'E, 3420 m water depth) The core stratigraphy, obtained from oxygen isotopic composition of planktonic and benthic foraminifera, indicates a continuous and undisturbed sedimentary record from the end of the last glacial period to present. Benthic foraminiferal study, using Principal Component Analysis, and 513C isotopic measurement were performed to assess the variability of palaeoproductivity and bottom-water ventilation changes across the last deglaciation in the Southern Indian Ocean. Our results show that depletion in δ13C occurring during the last deglaciation is due to a shift from highly ventilated bottom-water conditions during the Holocene to lower ventilated bottom-water conditions during the last glacial. For instance, faunal results show that trends in δ13C and assemblage distribution patterns present a strong link. Evolution from high δ13C values of the Holocene to the low values of δ13C during the last glacial maximum appear to be concomitant with an evolution from oligotrophic settings to more eutrophic conditions in the last glacial maximum where high organic matter and low oxygen concentrations occurred, leading to the dominance of low-oxygen tolerant infaunal taxa. δ13C isotopic measurement were performed to assess the variability of palaeoproductivity and bottom-water ventilation changes across the last deglaciation in the Southern Indian Ocean. Our results show that depletion in δ13C occurring during the last deglaciation is due to a shift from highly ventilated bottom-water conditions during the Holocene to lower ventilated bottom-water conditions during the last glacial. For instance, faunal results show that trends in δ13C and assemblage distribution patterns present a strong link. Evolution from high δ13C values of the Holocene to the low values of δ13C during the last glacial maximum appear to be concomitant with an evolution from oligotrophic settings to more eutrophic conditions in the last glacial maximum where high organic matter and low oxygen concentrations occurred, leading to the dominance of low-oxygen tolerant infaunal taxa. LSCE -CNRS/CEA Research Laboratory, Gif-sur-Yvette, FRANCE