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Walter, Hans-Jürgen; Rutgers van der Loeff, Michiel M; Francois, Roger (1999): Compilation of 231Protactinium/230 Thorium excess ratios in various surface sediment samples from the South Atlantic. PANGAEA, https://doi.org/10.1594/PANGAEA.55674, Supplement to: Walter, H-J et al. (1999): Reliability of the 231Pa/230Th Activity Ratio as a Tracer for Bioproductivity of the Ocean. In: Fischer, G & Wefer, G (eds.), Use of Proxies in Paleoceanography - Examples from the South Atlantic, Springer, Berlin, Heidelberg, 393-408

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Abstract:
In large areas of the world's oceans, there is a relationship between the mass flux of particulate matter and the unsupported 231Pa/230Th (xs231Pa/xs230Th) activity ratio of recent sediments. This observation forms the basis for using the xs231Pa/xs230Th ratio as a proxy for past changes in export productivity. However, a simple relationship between xs231Pa/xs 230Th ratio and particle flux requires that the water residence time in an ocean basin is far in excess of the scavenging residence time of 231Pa, and that the composition of sinking particles maintains a strong preference for the adsorption of 230Th over 231Pa with a constant 230Th/231Pa fractionation factor (F). The best correlation between xs231Pa/xs230Th ratio and mass flux is found in the Pacific Ocean. In the Atlantic, the contrast in the xs231Pa/xs230Th ratios between open ocean (low flux regions) and ocean margins (high flux regions) is much less pronounced due to the shorter residence time of deep water, resulting in less effective boundary scavenging of 231Pa. In the Southern Ocean, south of the Polar Front, there is no more a simple relationship between xs231Pa/xs230Th and particle flux. This is a result of a southward decrease in F, probably reflecting the increased opal content of sinking particles. Opal does not fractionate 231Pa and 230Th significantly. This lack of fractionation results in high xs231Pa/xs230Th ratios in opal-dominated regions, even in areas of very low particle fluxes such as the Weddell Sea. The xs231Pa/xs230Th ratio can therefore only be used as a paleoproductivity proxy if, in the time interval of interest, changes in the basin ventilation rate and differential scavenging of both radionuclides due to changes in the chemical composition of particulate matter can be excluded.
Project(s):
Marine Geochemistry @ AWI (AWI_MarGeoChem)
South Atlantic in Late Quaternary: Reconstruction of Budget and Currents (SFB261)
Coverage:
Median Latitude: -7.143739 * Median Longitude: -121.539218 * South-bound Latitude: -76.413300 * West-bound Longitude: 0.000000 * North-bound Latitude: 77.460000 * East-bound Longitude: -3.206670
Minimum Elevation: 0.0 m * Maximum Elevation: 0.0 m
Event(s):
SURWalter1999 * Elevation Start: 0.0 m * Elevation End: 0.0 m * Campaign: compiled data * Method/Device: Multiple investigations (MULT) * Comment: This is a virtual site to link a compiled data set from ocean bottom sediments
Parameter(s):
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
1Sample code/labelSample labeldata compiled from different sources
2LATITUDELatitudeGeocode
3LONGITUDELongitudeGeocode
4Depth, top/minDepth topmdata compiled from different sources
5Depth, bottom/maxDepth botmdata compiled from different sources
6Protactinium 231/Thorium 230 excess231Pa/230Th xssee reference(s)data compiled from different sources
7Protactinium 231/Thorium 230 excess, standard deviation231Pa/230Th xs std dev±see reference(s)data compiled from different sources
8Reference/sourceReferenceWalter, Hans-Jürgen
Size:
1917 data points

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