 |
| Titel |
Distribution of 230Thxs and 231Paxs in sediment particle classes of opal-rich and carbonate-rich sediments |
| VerfasserIn |
S. Kretschmer, S. Kusch, W. Geibert, M. Rutgers van der Loeff, G. Mollenhauer |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250026367
|
|
|
|
|
|
| Zusammenfassung |
| In many paleoceanographic studies 230Thexcess-normalization and the 231Paexcess/230Thexcess-ratio
are used as tools for reconstruction of particle fluxes and ocean circulation. 230Thxs and
231Paxs analyses are usually performed on bulk sediment samples. However, it is conceivable
that these two particle-reactive radioisotopes are not equally distributed between the
sedimentary components of bulk sediments, because Th and Pa show preferential adsorption
to specific particle types (e.g. Geibert and Usbeck, 2004). This is particularly relevant for
opal-rich sediments.
Lateral transport during particle settling exerts a sorting effect on particles according to
different grain size classes and sinking velocities, thus affecting the sedimentary
isotopesignal as well. This process may affect the applicability of 231Paxs and 230Thxs as
particle flux tracers. Currently discussed problems such as apparently high focusing
factors in the Panama Basin, or the applicability of 231Paxs/230Thxs-ratios for the
reconstruction of ocean circulation patterns might be related to this particle sorting
effect.
For this study we performed particle size specific analyses of 230Thxs and 231Paxs on
deep sea sediment samples from contrasting sedimentary settings, including the subtropical
Atlantic Ocean (Walvis Ridge), the Southern Ocean and the tropical Pacific Ocean (Panama
Basin). Bulk sediments were split into distinct particle size and density classes by sieving and
settling. In opal-rich and carbonate-rich sediment, most of the 230Thxs is bound within the
particle size class |
|
|
|
|
|
|