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| Titel |
Late Pleistocene glacial–interglacial shell-size–isotope variability in planktonic foraminifera as a function of local hydrography |
| VerfasserIn |
B. Metcalfe, W. Feldmeijer, M. de Vringer-Picon, G.-J. A. Brummer, F. J. C. Peeters, G. M. Ganssen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 15 ; Nr. 12, no. 15 (2015-08-07), S.4781-4807 |
| Datensatznummer |
250118059
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| Publikation (Nr.) |
 copernicus.org/bg-12-4781-2015.pdf |
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| Zusammenfassung |
| So-called "vital effects" are a collective term for a suite of physiologically
and metabolically induced variability in oxygen (δ18O) and carbon
(δ13C) isotope ratios of planktonic foraminifer shells that hamper
precise quantitative reconstruction of past ocean parameters. Correction for
potential isotopic offsets from equilibrium or the expected value is
paramount, as too is the ability to define a comparable life stage for each
species that allows for direct comparison. Past research has focused upon
finding a specific size range for individual species in lieu of other
identifiable features, thus allowing ocean parameters from a particular constant
(i.e. a specific depth or season) to be reconstructed. Single-shell isotope
analysis of fossil shells from a mid-latitude North Atlantic Ocean
piston core covering Termination III (200 to 250 ka) highlight the
advantage of using a dynamic size range, i.e. utilising measurements from
multiple narrow sieve size fractions spanning a large range of total body
sizes, in studies of palaeoclimate. Using this methodology, we show that
isotopic offsets between specimens in successive size fractions of
Globorotalia inflata and Globorotalia truncatulinoides are
not constant over time, contrary to previous findings. For δ18O in
smaller-sized globorotalids (212–250 μm) it is suggested that the
offset from other size fractions may reflect a shallower habitat in an early
ontogenetic stage. A reduction in the difference between small and large
specimens of G. inflata between insolation minima and maxima is
interpreted to relate to a prolonged period of reduced water column
stratification. For the shallow-dwelling species Globigerina
bulloides, no size–isotope difference between size fractions is observed, and
the variability in the oxygen isotopic values is shown to correlate well
with the seasonal insolation patterns. As such, patterns in oxygen isotope
variability of fossil populations may be used to reconstruct past seasonality
changes. |
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