Unknown
PANGAEA
In:
Supplement to: Missiaen, Lise; Pichat, Sylvain; Waelbroeck, Claire; Douville, Eric; Bordier, Louise; Dapoigny, Arnaud; Thil, François; Foliot, Lorna; Wacker, Lukas (2018): Downcore Variations of Sedimentary Detrital (238U/232Th) Ratio: Implications on the Use of 230Thxs and 231Paxs to Reconstruct Sediment Flux and Ocean Circulation. Geochemistry, Geophysics, Geosystems, 19, https://doi.org/10.1029/2017GC007410
Publication Date:
2023-06-27
Description:
Excess 231 Pa and 230 Th ( 231 Pa xs and 230 Th xs ) can be used to reconstruct past oceanic sedimentation ( 230 Th-normalized flux) and circulation changes (( 231 Pa/ 230 Th) xs,0 , hereafter Pa/Th). These quantities are determined by computing the detrital and authigenic contributions from bulk sediment measurement. The method relies on the use of a chosen constant value of the detrital ( 238 U/ 232 Th) activity ratio (hereafter (U/Th) det ). In this study, we have extracted the detrital fraction of the sediments from North Atlantic deep-sea core SU90-08 (43°03'1N, 30°02'5W, 3080m) and determined its (U/Th) det value over the last 40 ky. We find that (U/Th) det varied significantly through time with a minimum value of 0.4 during the Holocene and a maximum value of 0.7 during the Last Glacial Maximum (LGM). The sensitivity of sedimentary 230 Th-normalized flux and Pa/Th is tested for our study site and for other North-Atlantic sites. We show that the sensitivity is highly dependent on the core location and its terrigenous material supply. The 230 Th-normalized flux and Pa/Th signals are very robust in cores with low detrital contributions, whereas they are very sensitive to (U/Th) det changes in cores with higher detrital contribution. In the latter case, changes in 230 Th-normalized flux and Pa/Th due to the choice of a constant (U/Th) det can largely exceed the uncertainty on the 230 Th-normalized flux and Pa/Th, inducing potential biases in the amplitude and temporal variability of reconstructed sedimentation and ocean circulation changes.
Keywords:
Le Suroît; North Atlantic; PALEOCINAT; PC; Piston corer; SU90-08
Type:
Dataset
Format:
application/zip, 6 datasets
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