HR: 0830h
AN: PP11A-0204 [PDF]
TI: Variability of Shell Mass, $\delta$$^{18}$O and Mg/Ca in Planktonic Foraminifera: From Production to
Preservation
AU: * Anand, P
EM: palj@geo.vu.nl
AF: Paleoecology and Paleoclimatology, Vrije Universiteit, De Boelelaan 1085, Amsterdam, 1081 HV
Netherlands
AU: Ganssen, G
EM: gang@geo.vu.nl
AF: Paleoecology and Paleoclimatology, Vrije Universiteit, De Boelelaan 1085, Amsterdam, 1081 HV
Netherlands
AU: Elderfield, H
EM: he101@esc.cam.ac.uk
AF: Department of Earth Sciences, Downing Street, University of Cambridge, Cambridge, CB2 3EQ
United Kingdom
AU: Peeters, F
EM: peef@geo.vu.nl
AF: Paleoecology and Paleoclimatology, Vrije Universiteit, De Boelelaan 1085, Amsterdam, 1081 HV
Netherlands
AU: Kroon, D
EM: kroo@geo.vu.nl
AF: Paleoecology and Paleoclimatology, Vrije Universiteit, De Boelelaan 1085, Amsterdam, 1081 HV
Netherlands
AU: Jung, S
EM: jung@geo.vu.nl
AF: Paleoecology and Paleoclimatology, Vrije Universiteit, De Boelelaan 1085, Amsterdam, 1081 HV
Netherlands
AB:
Mg/Ca in planktonic foraminifera tests is now well established as a temperature proxy for surface and near-surface waters.
Yet work remains to be carried out to define the post-depositional processes affecting foraminiferal Mg/Ca after water-column
production. The advantage of Mg/Ca over other paleotemperature proxies is that it can be coupled with $\delta$$^{18}$O
measured on the same foraminiferal sample so as to determine seawater $\delta$$^{18}$O. We present results of a study of the
effect of dissolution on both Mg/Ca and $\delta$$^{18}$O of several planktonic foraminiferal species along a depth transect
($\sim$ 450-4000 m) off Somalia, spanning the lysocline at $\sim$ 2000 m.
The planktonic foraminiferal species, {\it Globigerinoides ruber}, {\it Globigerina bulloides}, {\it Globigerinoides
sacculifer} and {\it Neogloboquadrina dutertrei} were analysed for average shell mass, Mg/Ca, Sr/Ca, $\delta$$^{18}$O and
$\delta$$^{13}$C from core-top samples from 250-300 $\mu$m size fraction from a depth transect off Somalia (water depth range
for samples: $\sim$ 450-4000 m). The average shell mass decreases by 10 % in {\it G. ruber}, 19 % in {\it N. dutertrei},
29 % in {\it G. bulloides} and 37 % in {\it G. sacculifer} below the lysocline. {\it N. dutertrei} is the only species
which shows a significant decrease in both $\delta$$^{18}$O (from -0.61 to -0.25 $\permil$) and Mg/Ca (from 2.57 $\pm$ 0.47
to 1.10 mmol/mol). Only a small decrease in Mg/Ca is found in {\it G. sacculifer} (from 3.50 $\pm$ 0.07 to 3.08 mmol/mol),
{\it G. bulloides} (from 4.84 $\pm$ 0.20 to 4.39 mmol/mol) and {\it G. ruber} (from 4.49 $\pm$ 0.24 to 4.17 mmol/mol) below
the lysocline. The $\delta$$^{18}$O and Mg/Ca of {\it G. ruber} are least affected by dissolution and hence is the most
useful species for surface water temperature reconstructions at this site. Data from the water column and the sediment record
for {\it G. ruber} and {\it N. dutertrei} will serve to quantify the fate of shell mass, $\delta$$^{18}$O and Mg/Ca proxies
from production to preservation.
UR: http://www.geo.vu.nl/users/pal/staff/palj.htm
DE: 1065 Trace elements (3670)
DE: 1615 Biogeochemical processes (4805)
DE: 3344 Paleoclimatology
DE: 4267 Paleoceanography
DE: 4825 Geochemistry
SC: Paleoceanography and Paleoclimatology [PP]
MN: 2003 Fall Meeting