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  • 1
    Publication Date: 2022-07-25
    Description: The Th content of the sediment samples from "Meteor" core 12310 (3080 m water depth, off NW Africa) on a carbonate-free basis lies around the average of 12.4 ppm and is similar to the average content of the earth crust. On the contrary, uranium was found to be up to 3.5-fold enriched in the core section between 60 and 330 cm (within the Würm Glacial) where reducing conditions occur, due to deposition of authigenic uranium (9 µg/cm2 1000 yrs.). The authigenic uranium content is correlated to the organic matter content (U/Corg ratio = 6 · 10-4). On the basis of the uranium content of the oxidized section uranium was split into a detritic and an authigenic component and the amount of supported ionium was calculated. From the profile of the specific I0.excess act1v1ty Io-total - Io-supported) with depth, average sedimentation rates of 3.3 ± 0.6 cm/1000 yrs. for the warmer stages and of 5 ± 1 cm/1000 yrs. for the cooler periods were estimated.
    Type: Article , PeerReviewed
    Format: text
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  • 2
    Publication Date: 2022-07-25
    Description: A rapid procedure for Io (Th230) dating of sediments with accumulation rates in the range of several cm/1000 years is described. Studying of large sample populations with very small Io-excess activity is possible as the counting time (around 1500 min/sample) are 2 to 5 times shorter than with the standard Io-excess method. Improved sensitivity of the Io-excess measurement is achieved by: 1) extraction (~90%) of the authigenic Io-excess with EDTA, with minor leaching (~30%) of the allogenic Th232 and Io-supported, 2) processing samples as large as 10 g or more. The procedure was applied to sediments from the Caribbean (V 12-122) and from the Ionian Sea (22M48 and 17M17). In the case of the standard core V 12-122 our results are in good agreement with previous time-consuming Io determinations. The resulting average accumulation rates of 2.0 ± 0.3 cm/1000 years for the Ionian Sea cores are close to the average derived from magnetic reversal studies of a nearby core.
    Type: Article , PeerReviewed
    Format: text
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