Sr/Ca in Calcitic Tests of Benthic Foraminifera - A Potential Water-Depth Proxy?
Peer reviewed, Journal article
Published version
Permanent lenke
https://hdl.handle.net/1956/4489Utgivelsesdato
2009Metadata
Vis full innførselSamlinger
- Department of Earth Science [1040]
Originalversjon
https://doi.org/10.2174/1874262900903010090Sammendrag
Well-preserved low-Mg calcite tests of modern benthic foraminifera from a depth transect off SW Norway show decreasing Sr/Ca with increasing water depth (r = –0.84). The Mg/Ca ratios also decrease with increasing water depth, although in a curvilinear fashion. Moreover, the inter- and intra-species scatter is apparently larger than for Sr/Ca. A majority of the analysed specimens have Mn/Ca < 200 μmol/mol, and show Sr/Ca, Mg/Ca that fall within published ranges for benthic foraminiferal calcite, indicating that pristine biogenic calcite has been analysed. The uniform temperature and salinity of bottom waters below ~800 m moreover indicate that neither temperature nor salinity can explain the observed Me/Ca trends. The Sr/Ca and Mg/Ca depth trends cannot be explained by dissolution since bottom waters are generally supersaturated with respect to calcite, and dissolution is only observed in a few specimens. Moreover, a regular increase in sedimentary organic content with depth needed to invoke a decrease in porewater pH and concomittant calcite dissolution is not observed. We tentatively ascribe the decreasing Sr/Ca and Mg/Ca trends to depthrelated physiological phenomena. The relatively small intra- and interspecies scatter at a given water depth, as well as the linear decrease in Sr/Ca ratios with increasing water depth observed in modern oceans, may render the Sr/Ca in calcitic benthic foraminifera a potential water-depth proxy for fossil deposits.
Utgiver
Bentham OpenOpphavsrett
Sælen et al.Copyright Sælen et al.; Licensee Bentham Open.