Encrustation and trace element composition of Neogloboquadrina dutertrei assessed from single chamber analyses : implications for paleotemperature estimates
Jonkers, Lukas (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Nooijer, L. J. de (Rijksuniversiteit te Utrecht. Department of Geochemistry)
Reichart, G. J. (Rijksuniversiteit te Utrecht. Department of Geochemistry)
Zahn, Rainer (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals)
Brummer, Geert-Jan (Koninklijk Nederlands Instituut voor Onderzoek der Zee. Department of Marine Geology)

Fecha:	2012
Resumen:	Crust formation is a common phenomenon in planktonic foraminifera. Because of their different formation mechanism and hence composition, crusts affect the overall test composition and therefore complicate the use of crust-bearing foraminifera in paleoceanography. Such species are often used to estimate subsurface paleotemperatures, and although the influence of encrustation on the trace element/Ca ratio is recognised, it has not been systematically explored between and within tests. Here we use laser ablation ICP-MS to assess the variability in trace element composition of the crust of Neogloboquadrina dutertrei within individual chambers, as well as the effect of compositional heterogeneity of the crust on whole test chemistry. Compositionally, the outer crust differs from inner layer by lower Mg/Ca and Mn/Ca, but is indistinguishable in Sr/Ca. Crust thickness decreases towards the younger chambers, and it may be entirely absent from the last chamber. In contrast to Mn/Ca and Sr/Ca, crustal Mg/Ca ratios show a tendency towards higher values on the younger chambers. These patterns in crust thickness and in crust Mg/Ca indicate that temperature is not the dominant factor controlling crust composition. Temperature estimates based on N. dutertrei, and presumably other crust-forming species too, are therefore biased towards too low values. Through comparison of modern and glacial tests, we show that this bias is not constant and that changes in crust thickness and/or in Mg/Ca values can spuriously suggest temperature changes.
Nota:	Es va publicar la discussió prèvia a la publicació a Biogeoscience Discussion, 2012, vol 9, p. 10615-10644 (doi:10.5194/bgd-9-10615-2012)
Derechos:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Lengua:	Anglès
Documento:	Article ; recerca ; Versió publicada
Materia:	Plàncton ; Paleoclimatologia ; Planktonic foraminifera ; Foraminífers planctònics ; Neogloboquadrina dutertrei ; Paleotemperature ; Paleotemperatura
Publicado en:	Biogeosciences, Vol. 9 Issue 11 (2012) , p. 4851-4860, ISSN 1726-4189

DOI: 10.5194/bg-9-4851-2012

Geosciences 10 p, 1.9 MB

Geosciences discussion 30 p, 2.0 MB

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