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Enrichment of dissolved silica in the deep equatorial Pacific during the Eocene-Oligocene

Fontorbe, Guillaume LU ; Frings, Patrick J. LU ; De La Rocha, Christina L. LU ; Hendry, Katharine R.; Carstensen, Jacob and Conley, Daniel J. LU (2017) In Paleoceanography
Abstract

Silicon isotope ratios (expressed as δ30Si) in marine microfossils can provide insights into silica cycling over geologic time. Here we used δ30Si of sponge spicules and radiolarian tests from the Paleogene Equatorial Transect (Ocean Drilling Program Leg 199) spanning the Eocene and Oligocene (~50-23 Ma) to reconstruct dissolved silica (DSi) concentrations in deep waters and to examine upper ocean δ30Si. The δ30Si values range from -3.16 to +0.18‰ and from -0.07 to +1.42‰ for the sponge and radiolarian records, respectively. Both records show a transition toward lower δ30Si values around 37 Ma. The shift in radiolarian δ30Si is interpreted as a consequence of changes in... (More)

Silicon isotope ratios (expressed as δ30Si) in marine microfossils can provide insights into silica cycling over geologic time. Here we used δ30Si of sponge spicules and radiolarian tests from the Paleogene Equatorial Transect (Ocean Drilling Program Leg 199) spanning the Eocene and Oligocene (~50-23 Ma) to reconstruct dissolved silica (DSi) concentrations in deep waters and to examine upper ocean δ30Si. The δ30Si values range from -3.16 to +0.18‰ and from -0.07 to +1.42‰ for the sponge and radiolarian records, respectively. Both records show a transition toward lower δ30Si values around 37 Ma. The shift in radiolarian δ30Si is interpreted as a consequence of changes in the δ30Si of source DSi to the region. The decrease in sponge δ30Si is interpreted as a transition from low DSi concentrations to higher DSi concentrations, most likely related to the shift toward a solely Southern Ocean source of deep water in the Pacific during the Paleogene that has been suggested by results from paleoceanographic tracers such as neodymium and carbon isotopes. Sponge δ30Si provides relatively direct information about the nutrient content of deep water and is a useful complement to other tracers of deep water circulation in the oceans of the past.

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author
organization
publishing date
type
Contribution to journal
publication status
epub
subject
keywords
Eocene Oligocene, Ocean circulation, Silicon isotopes
in
Paleoceanography
publisher
American Geophysical Union
external identifiers
  • scopus:85027533186
ISSN
0883-8305
DOI
10.1002/2017PA003090
language
English
LU publication?
yes
id
65596d30-a847-49d9-beb3-0094a51b67a5
date added to LUP
2017-09-15 12:08:39
date last changed
2017-09-15 12:08:39
@article{65596d30-a847-49d9-beb3-0094a51b67a5,
  abstract     = {<p>Silicon isotope ratios (expressed as δ<sup>30</sup>Si) in marine microfossils can provide insights into silica cycling over geologic time. Here we used δ<sup>30</sup>Si of sponge spicules and radiolarian tests from the Paleogene Equatorial Transect (Ocean Drilling Program Leg 199) spanning the Eocene and Oligocene (~50-23 Ma) to reconstruct dissolved silica (DSi) concentrations in deep waters and to examine upper ocean δ<sup>30</sup>Si. The δ<sup>30</sup>Si values range from -3.16 to +0.18‰ and from -0.07 to +1.42‰ for the sponge and radiolarian records, respectively. Both records show a transition toward lower δ<sup>30</sup>Si values around 37 Ma. The shift in radiolarian δ<sup>30</sup>Si is interpreted as a consequence of changes in the δ<sup>30</sup>Si of source DSi to the region. The decrease in sponge δ<sup>30</sup>Si is interpreted as a transition from low DSi concentrations to higher DSi concentrations, most likely related to the shift toward a solely Southern Ocean source of deep water in the Pacific during the Paleogene that has been suggested by results from paleoceanographic tracers such as neodymium and carbon isotopes. Sponge δ<sup>30</sup>Si provides relatively direct information about the nutrient content of deep water and is a useful complement to other tracers of deep water circulation in the oceans of the past.</p>},
  author       = {Fontorbe, Guillaume and Frings, Patrick J. and De La Rocha, Christina L. and Hendry, Katharine R. and Carstensen, Jacob and Conley, Daniel J.},
  issn         = {0883-8305},
  keyword      = {Eocene Oligocene,Ocean circulation,Silicon isotopes},
  language     = {eng},
  month        = {08},
  publisher    = {American Geophysical Union},
  series       = {Paleoceanography},
  title        = {Enrichment of dissolved silica in the deep equatorial Pacific during the Eocene-Oligocene},
  url          = {http://dx.doi.org/10.1002/2017PA003090},
  year         = {2017},
}