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A record of Neogene seawater δ11B reconstructed from paired δ11B analyses on benthic and planktic foraminifera

A record of Neogene seawater δ11B reconstructed from paired δ11B analyses on benthic and planktic foraminifera
A record of Neogene seawater δ11B reconstructed from paired δ11B analyses on benthic and planktic foraminifera
The boron isotope composition (δ11B) of foraminiferal calcite reflects the pH and the boron isotope composition of the seawater the foraminifer grew in. For pH reconstructions, the δ11B of seawater must therefore be known, but information on this parameter is limited. Here we reconstruct Neogene seawater δ11B based on the δ11B difference between paired measurements of planktic and benthic foraminifera and an estimate of the coeval water column pH gradient from their δ13C values. Carbon cycle model simulations underscore that the ΔpH–Δδ13C relationship is relatively insensitive to ocean and carbon cycle changes, validating our approach. Our reconstructions suggest that δ11Bsw was  ∼  37.5 ‰ during the early and middle Miocene (roughly 23–12 Ma) and rapidly increased during the late Miocene (between 12 and 5 Ma) towards the modern value of 39.61 ‰. Strikingly, this pattern is similar to the evolution of the seawater isotope composition of Mg, Li and Ca, suggesting a common forcing mechanism. Based on the observed direction of change, we hypothesize that an increase in secondary mineral formation during continental weathering affected the isotope composition of riverine input to the ocean since 14 Ma.
1814-9332
149-170
Greenop, Rosanna
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Hain, Mathis
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Sosdian, Sindia M.
718c374a-7460-4c7e-a616-f93b1f0a46a5
Oliver, Kevin
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Goodwin, Philip
87dbb154-5c39-473a-8121-c794487ee1fd
Chalk, Thomas
0021bbe6-6ab1-4a30-8542-654d0f2d1a0a
Lear, Caroline H.
c0caf74d-ed6c-4b04-b5c8-de8fc794943c
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Foster, Gavin
fbaa7255-7267-4443-a55e-e2a791213022
Greenop, Rosanna
9a08d945-03bb-41b9-b8f2-f6e84731057e
Hain, Mathis
d31486bc-c473-4c34-a814-c0834640876c
Sosdian, Sindia M.
718c374a-7460-4c7e-a616-f93b1f0a46a5
Oliver, Kevin
588b11c6-4d0c-4c59-94e2-255688474987
Goodwin, Philip
87dbb154-5c39-473a-8121-c794487ee1fd
Chalk, Thomas
0021bbe6-6ab1-4a30-8542-654d0f2d1a0a
Lear, Caroline H.
c0caf74d-ed6c-4b04-b5c8-de8fc794943c
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Foster, Gavin
fbaa7255-7267-4443-a55e-e2a791213022

Greenop, Rosanna, Hain, Mathis, Sosdian, Sindia M., Oliver, Kevin, Goodwin, Philip, Chalk, Thomas, Lear, Caroline H., Wilson, Paul A. and Foster, Gavin (2017) A record of Neogene seawater δ11B reconstructed from paired δ11B analyses on benthic and planktic foraminifera. Climate of the Past, 13 (2), 149-170. (doi:10.5194/cp-13-149-2017).

Record type: Article

Abstract

The boron isotope composition (δ11B) of foraminiferal calcite reflects the pH and the boron isotope composition of the seawater the foraminifer grew in. For pH reconstructions, the δ11B of seawater must therefore be known, but information on this parameter is limited. Here we reconstruct Neogene seawater δ11B based on the δ11B difference between paired measurements of planktic and benthic foraminifera and an estimate of the coeval water column pH gradient from their δ13C values. Carbon cycle model simulations underscore that the ΔpH–Δδ13C relationship is relatively insensitive to ocean and carbon cycle changes, validating our approach. Our reconstructions suggest that δ11Bsw was  ∼  37.5 ‰ during the early and middle Miocene (roughly 23–12 Ma) and rapidly increased during the late Miocene (between 12 and 5 Ma) towards the modern value of 39.61 ‰. Strikingly, this pattern is similar to the evolution of the seawater isotope composition of Mg, Li and Ca, suggesting a common forcing mechanism. Based on the observed direction of change, we hypothesize that an increase in secondary mineral formation during continental weathering affected the isotope composition of riverine input to the ocean since 14 Ma.

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More information

Accepted/In Press date: 9 January 2017
e-pub ahead of print date: 24 February 2017
Published date: 24 February 2017
Organisations: Ocean and Earth Science, Geochemistry, Physical Oceanography, Paleooceanography & Palaeoclimate

Identifiers

Local EPrints ID: 406999
URI: http://eprints.soton.ac.uk/id/eprint/406999
ISSN: 1814-9332
PURE UUID: 4b069152-1b72-4a53-a19e-d16ee04de1c7
ORCID for Thomas Chalk: ORCID iD orcid.org/0000-0002-2880-3847
ORCID for Gavin Foster: ORCID iD orcid.org/0000-0003-3688-9668

Catalogue record

Date deposited: 29 Mar 2017 01:09
Last modified: 18 Feb 2021 17:29

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