HR: 0800h
AN: PP11A-0540    [Abstracts]
TI: Refining Of The MIS 5 Tephrostratigraphic Record In Marine Cores From The S-Norwegian Margin; A Tool For High-Resolution Dating And Correlation Of Climatic Archives
AU: * Brendryen, J
EM: Jo.Brendryen@student.uib.no
AF: University of Bergen, Dept. of Earth Science, Allegt. 41, Bergen, 5007
AU: Haflidason, H
EM: Haflidi.Haflidason@geo.uib.no
AF: University of Bergen, Dept. of Earth Science, Allegt. 41, Bergen, 5007
AB: Tephrochronology has proved to be an excellent tool for correlation and dating of sediment sequences of various ages and in different archives. It is, however, well known that the limitation of applying tephra from the whole range of basaltic eruptions, taking place in Iceland during is partly due to the distribution and thickness of some of these tephra layers but importantly also due to the geochemical identification of these tephra layers. Knowing that during at least the last 1100 years has the frequency of volcanic eruption in Iceland been of an order of one eruption every 5th year, the potential for utilising the entire tephrostratigraphic record for dating and correlation is great. Still only few tephra layers have been applied for dating and correlation from this period as ca. 90 % of these tephra layers are originated from basaltic volcanoes where the geochemical identification has been a limited factor due to internal homogeneity within the basaltic volcanic systems. A new analytical method, which uses a broader spectrum of geochemical elements as the tracer and the rare earth elements REE, will offer new possibilities to identify each of these basaltic layers on a single grain basis. This method will offer a great possibility to extend the application of the tephra records significantly as a dating and correlation tool especially where these tephra events can be combined with spectra obtained through e.g. stable isotope analyses or through non-destructive core detection. Here, Marine Isotope Stage 5, MIS 5, tephra layers in two giant piston cores, i.e. MD99-2283 and MD99-2289 from the S-Norwegian Margin, have been identified and analysed geochemically for major, trace and REE. The EMP (electron microprobe) technique has been applied on the major elements and Laser Ablation ICP-MS (213 nm) on the trace and the REE. At least 14 tephra layers, both previously described and identified, have been found and will be presented. These findings are used to correlate the two cores and other sediment/ice core sequences from the same time span, and to resolve the timing of important climatic changes in MIS 5. The application of Laser Ablation ICP-MS on geological fingerprinting problems will also be discussed.
DE: 8404 Ash deposits
DE: 3344 Paleoclimatology
DE: 3655 Major element composition
DE: 3022 Marine sediments--processes and transport
DE: 1749 Volcanology, geochemistry, and petrology
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2004 AGU Fall Meeting