Publication Date:
2024-01-09
Description:
The Labrador Sea is a particularly suitable high-latitude basin for investigating U and Th behavior in deep-sea sediments. During the late Quaternary, the cyclic development and decay of huge ice sheets on adjacent land masses resulted in large-amplitude changes in sedimentation rates and organic paleoproductivities. The resulting magnification of U and Th response is well illustrated by high-resolution studies on piston-cored sediments from the Greenland continental rise at Ocean Drilling Program Leg 105 Site 646 spanning isotopic stages 8 to 1. Our results show a clear positive correlation of 238U/232Th ratios with organic paleoproductivity indicators (e.g., dinocyst) due to U uptake in the water column and/or during the early early diagenesis of organic matter responding to carbon fluxes and to their climate forcing. 230Th excesses over 234U exceed the theoretical value of the 230Th rain from the overlying water column, indicating lateral input possibly from the Greenland slope and shelf. Because these horizontal fluxes of 230Th may be partly controlled by physical parameters, 230Th excesses cannot be unequivocally correlated with sedimentation rates and/or productivity as reported elsewhere. In this subarctic basin characterized by low overall organic carbon burial, the 238U/232Th ratio appears to be a sensible geochemical indicator of organic activity and paleoproductivity.
Keywords:
105-646B; AGE; Age, error; Alpha spectrometry; Calculated; DRILL; Drilling/drill rig; DSDP/ODP/IODP sample designation; Joides Resolution; Labrador Sea; Leg105; Ocean Drilling Program; ODP; Sample, optional label/labor no; Sample code/label; Thorium-230; Thorium-230/Thorium-232 ratio; Thorium-230/Thorium-232 ratio error; Thorium-230/Uranium-234 activity ratio; Thorium-230/Uranium-234 activity ratio, standard deviation; Thorium-232; Thorium-232, standard deviation; Uranium-234/Uranium-238 activity ratio; Uranium-234/Uranium-238 activity ratio, standard deviation; Uranium-238; Uranium-238, standard deviation; Uranium-238/Thorium-232 ratio; Uranium-238/Thorium-232 ratio error
Type:
Dataset
Format:
text/tab-separated-values, 352 data points
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