Abstract
Stable isotopes and trace elements in foraminifera shells are important for determining the paleochemistry of the ocean, and Mg/Ca ratios and δ18O values in foraminifera have recently been used to determine simultaneously the temperature and salinity of past oceans. However, large variations between species and significant Mg intra-shell heterogeneity Indicate a major role for biological factors in determining the Mg/Ca ratio in foraminifera. Our novel in vivo observations on the biomineralization process of perforate foraminifera show that their calcareous wall is composed of two different calcite types: a thin, high-Mg primary layer, and low-Mg layers that cover the primary layer on both sides. The data may suggest that two biomineralization pathways are employed in the formation of the different calcite types. A new conceptual framework is provided to explain part of the Mg heterogeneity in foraminiferal shells and the variable sensitivity of the Mg/Ca ratio to temperature in different species.
Original language | English |
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Pages (from-to) | 841-844 |
Number of pages | 4 |
Journal | Geology |
Volume | 33 |
Issue number | 11 |
DOIs | |
State | Published - Nov 2005 |
Keywords
- Biomineralization
- Foraminifera
- Mg/Ca ratio
- Paleotemperature
- Vital effects