Article (Scientific journals)
Advective excess Ba transport as shown from sediment and trap geochemical signatures
Fagel, Nathalie; André, Luc; Dehairs, Frank
1999In Geochimica et Cosmochimica Acta, 63 (16), p. 2353-2367
Peer Reviewed verified by ORBi
 

Files


Full Text
GCA Ba omex I 1999.pdf
Publisher postprint (782.58 kB)
Request a copy

All documents in ORBi are protected by a user license.

Send to



Details



Abstract :
[en] We report the results of a geochemical study of sediment and trap material. Major and trace elements (Zr, Ba, rare earth elements, and Th) were analyzed on bulk sedimentary material collected along the NE Atlantic margin. Our aim is to test the widespread use of Ba-barite as a proxy for paleoproductivity in a continental margin area. This environment is of great interest because atmospheric-oceanic exchanges are important. In sediments, the geochemical signatures remain close to an upper crust reference, with flat shale-normalized rare earth elements patterns and constant elementary ratios. The calculated biogenic fraction of Ba or excess Pa (20-45%) remains lower than the excess Ba record in trap material (80-99%). The evolution of the geochemical signature along the margin reflects variable dilution of a detrital Post Archean Australian Shale-like component by a biogenic carbonaceous seawater-derived component. The trap material displays a wide range of variation in its trace element content (e.g., Ba similar to 150-3000 ppm, Zr similar to 2-100 ppm), except for the abyssal site, which is characterized by constant signature. In the two other sites, all of the trace element contents increase with water depth and present pronounced seasonal changes at each sampled water depth. The amount of excess Ba also increases in the deepest traps, and its evolution throughout the year mimics the change of the other analyzed trace elements. In contrast, its relationships with particulate organic carbon are not obvious. In term of fluxes, two periods of enhanced excess Ba fluxes are observed: (1) excess Pa flux increases with the detrital-like elements like Th especially during winter, and (2) excess Pa flux is enhanced without any change for the other trace elements during spring. To explain the first case, a supply through lateral advection is proposed. Such transient input of significant excess Ba flux will have a great impact on the yearly averaged estimation of the export production. Indeed, only the second case reflects a bloom in the biological productivity of the water column and must be taken into account in a mean calculation of the export production. Finally, a normalization of the excess Ba by detrital-like element like Th will help to discriminate between a real increase of the excess Ba due to local productivity change (high excess Ba and high excess Ba/Th ratio greater than or equal to 10,000) and any input due to advection process (high excess Ba but low excess Ba/Th ratio < 2000). Copyright (C) 1999 Elsevier Science Ltd.
Research center :
MRAC
Disciplines :
Earth sciences & physical geography
Author, co-author :
Fagel, Nathalie  ;  Université de Liège - ULiège > Département de géologie > Argiles, géochimie et environnements sédimentaires
André, Luc
Dehairs, Frank
Language :
English
Title :
Advective excess Ba transport as shown from sediment and trap geochemical signatures
Publication date :
1999
Journal title :
Geochimica et Cosmochimica Acta
ISSN :
0016-7037
eISSN :
1872-9533
Publisher :
Pergamon Press - An Imprint of Elsevier Science, Oxford, United Kingdom
Volume :
63
Issue :
16
Pages :
2353-2367
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
SSTC - Services Fédéraux des Affaires Scientifiques, Techniques et Culturelles [BE]
Available on ORBi :
since 19 May 2010

Statistics


Number of views
42 (0 by ULiège)
Number of downloads
1 (1 by ULiège)

Scopus citations®
 
24
Scopus citations®
without self-citations
20
OpenCitations
 
23

Bibliography


Similar publications



Contact ORBi