HR: 0800h
AN: PP31C-0543    [Abstracts]
TI: Stable Strontium (δ^88/86Sr) and U-Th isotope systematics of cold-water corals: A combined proxy for Holocene changes of the Mediterranean outflow
AU: * Liebetrau, V
EM: vliebetrau@ifm-geomar.de
AF: IFM-GEOMAR, Leibniz Institute for Marine Sciences, Wischhofstr. 1-3, Kiel, 24148, Germany
AU: Rüggeberg, A
EM: arueggeberg@ifm-geomar.de
AU: Fietzke, J
EM: jfietzke@ifm-geomar.de
AU: Eisenhauer, A
EM: aeisenhauer@ifm-geomar.de
AU: Flögel, S
EM: sfloegel@ifm-geomar.de
AU: Linke, P
EM: plinke@ifm-geomar.de
AU: Schönfeld, J
EM: jschoenfeld@ifm-geomar.de
AB: The application of δ¹⁸O and Sr/Ca for temperature reconstruction on cold water corals has been shown to be restricted. Hence, the development and application of alternative proxies is highly desirable. This study combines the stable strontium isotope method (δ^88/86Sr, Fietzke and Eisenhauer (2006)) as a potential paleotemperature proxy with MIC-ICP-MS (multi ion counting – inductively coupled plasma – mass spectrometry) U-Th geochronolgy on cold-water corals from the central Gulf of Cadiz. The sampled reef structure in 1325 m depth on top of the Captain Arutyunov Mud Volcano (MV) consists predominantly of dead Lophelia pertusa, accompanied rarely by living solitary corals ( Dendrophyllia sp.). Potentially recorded environmental influences on these archives are significant water mass changes, e.g. variation of depth and intensity of the Mediterranean Outflow Water (MOW) due to climate changes, time intervals of marine methane emanation (surface-near gas-hydrate occurre close to the coral site) and the mud volcano activity itself. Assuming a temperature dependent strontium isotope fractionation during calcium carbonate precipitation temperatures were determined for the living solitary corals, ranging from 9 to 11.5 ° C (typical error: about 1 ° C). During sampling the bottom water temperature was 8.96 ° C and the lower MOW reached from 1075 to 1188 m depth with 10 to 10.5 ° C. First U-Th age data reflect slow growth rates of 0.13 to 0.25 mm/year for the solitary corals. However, the temperature correlation implies the stable strontium approach, which was originally deduced from reef building corals, as suitable for solitary species as well. For the fossil Lophelia pertusa colonies the actual δ^88/86Sr data set indicates a range from 7.5 to 13 ° C with a distinct U-Th age distribution over the last 10 ka, closely correlating with the water depth specific record of lower MOW published by Schönfeld and Zahn (2000). The implication of a lower MOW control on reef formation is supported by coincidence of its actual elevated position with the lack of living Lophelia pertusa at the sampling site. The stable strontium isotope ratio δ^88/86Sr of biogenic carbonates may serve as a new paleo-temperature proxy for reef-building and solitary deep-sea corals and thus introduce new perspectives in paleoceanography, such as changes in intermediate and deep-sea temperature and ocean circulation. Fietzke J. and Eisenhauer A. (2006), G-cubed 7 Q08009, doi:10.1029/2006GC001243. Schönfeld J. and Zahn R. (2000), Palaeogeography Palaeoclimatology, Palaeoecology 159, 85 – 111.
DE: 1040 Radiogenic isotope geochemistry
DE: 1041 Stable isotope geochemistry (0454, 4870)
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 4916 Corals (4220)
DE: 4924 Geochemical tracers
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2007 Fall Meeting