Open AccessVariability of Mg/Ca and Sr/Ca between and within the planktonic foraminifers Globigerina bulloides and Globorotalia truncatulinoides
Author(s) -
Anand Pallavi,
Elderfield Henry
Publication year - 2005
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2004gc000811
Subject(s) - globigerina bulloides , geology , electron microprobe , analytical chemistry (journal) , mineralogy , oceanography , chemistry , foraminifera , environmental chemistry , benthic zone
The variability in Mg/Ca and Sr/Ca within individual tests and chambers of tests, and samples consisting of differing numbers of individuals, was determined for Globigerina bulloides and Globorotalia truncatulinoides in a North Atlantic core top sample (52.918°N 16.917°W′). The variability in Mg/Ca and Sr/Ca within individual tests and chambers was determined by electron microprobe, and samples consisting of variable sample size were measured using inductively coupled plasma optical emission spectrometer (ICP‐OES). Large compositional heterogeneity was found within individual chambers, and within the test as a whole, of the two species and the presence of regions with up to ∼10 mmol/mol Mg/Ca, especially in G. bulloides. Mean Mg/Ca decreases in successive chambers of G. bulloides (especially the 300–355 μm fraction) and is accompanied by decreasing variance but is not statistical significant. Sr/Ca is much more homogeneously distributed, with a normal distribution, and shows no differences from chamber to chamber. The variability of Mg/Ca and Sr/Ca decreases with increasing sample size, from single to five to twenty tests per sample, approximately as for a normal distribution, with greater variability for G. bulloides than for G. truncatulinoides , equivalent to uncertainties in temperature (n = 20) of 1.1°C and 0.7°C for the two species within the whole of the sediment mixed layer.