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| Titel |
Transport of branched tetraether lipids from the Tagus River basin to the coastal ocean of the Portuguese margin: consequences for the interpretation of the MBT'/CBT paleothermometer |
| VerfasserIn |
C. Zell, J.-H. Kim, M. Balsinha, D. Dorhout, C. Fernandes, M. Baas, J. S. Sinninghe Damsté |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 11, no. 19 ; Nr. 11, no. 19 (2014-10-14), S.5637-5655 |
| Datensatznummer |
250117640
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| Publikation (Nr.) |
 copernicus.org/bg-11-5637-2014.pdf |
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| Zusammenfassung |
| Branched glycerol dialkyl glycerol tetraethers (brGDGTs), which are thought
to be transported from soil to marine sediment by rivers, have been used to
reconstruct the mean annual air temperature (MAAT) and soil pH of the
drainage basin using the methylation index of branched tetraethers (MBT,
recently refined as MBT') and cyclization index of branched tetraethers (CBT)
from coastal marine sediment records. In this study, we trace the
brGDGTs from source to sink in the Tagus River basin, the longest river
system on the Iberian Peninsula, by determining their concentration and
distribution in soils, river suspended particulate matter (SPM), riverbank
sediments, marine SPM, and marine surface sediments. The concentrations of
brGDGTs in river SPM were substantially higher and their distributions were
different compared to those of the drainage basin soils. This indicates that
brGDGTs are mainly produced in the river itself. In the marine environment,
the brGDGT concentrations rapidly decreased with increasing distance from the
Tagus estuary. At the same time, the brGDGT distributions in marine sediments
also changed, indicating that marine in situ production also takes place.
These results show that there are various problems that complicate the use of
the MBT'/CBT for paleoreconstructions using coastal marine sediments in
the vicinity of a river. However, if the majority of brGDGTs are produced in
the river, it might be possible to reconstruct the environmental (temperature
and pH) conditions of the river water using appropriate aquatic calibrations,
provided that marine core locations are chosen in such a way that the brGDGTs
in their sediments are predominantly derived from riverine in situ
production. |
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