Goldschmidt Conference Abstracts 2009 A229 Shona and Discovery seamount Uranium-lead dating of speleothems: chains, South Atlantic: Prospects and limitations Superplume source constraints R.A. CLIFF 1 2 C. CLASS * AND A.P. LE ROEX School of Earth & Environment, University of Leeds 1Lamont-Doherty Earth Observatory of Columbia University, In recent year several studies have shown that U-Pb Palisades, NY 10964, USA isotopic dating is a promising option for dating speleothems (*correspondence:
[email protected]) from the early Pleistocene and earlier which has otherwise 2University of Cape Town, Rondebosch 7701, South Africa presented a difficult challenge. (
[email protected]) The integrity of the U-Pb system has been confirmed by comparison of U-Pb and U-Th data on a speleothem from the The effectively un-sampled major bathymetric anomalies Spannagel Cave in the Austrian Alps. Disequilibrium- of the Shona Ridge – Meteor Rise – Agulhas Ridge – Cape corrected U-Pb ages date growth from 340 ka to 267 ka. High Rise and Discovery seamounts in the South Atlantic have been resolution sampling of one short growth interval yielded U-Pb attributed to the activity of the Shona and Discovery mantle and U-Th ages in close agreement at 266 ka with ± 1 ka error plumes based solely on geochemical signatures measured in on the U-Pb age. These results confirm closed system Mid-Ocean Ridge basalts from the adjacent Mid-Atlantic behaviour throughout the uranium decay chain even in such Ridge and a single Discovery Seamount sample. Here we U-rich samples. present new Sr-Nd-Pb-Hf isotope data on dredge samples Speleothems from the Wilder Mann and Wildmahd caves from these seamount chains collected by the ANT XXIII/5 in the Allgäu Alps, western Austria encapsulate a detailed cruise of the FS Polarstern.