Experimental paleotemperature equation for planktonic foraminifera |
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| Authors: | Jonathan Erez Boaz Luz |
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| Institution: | The Hebrew University of Jerusalem. The H. Steinitz Marine Biology Laboratory. Eilat, P.O. Box 469, Israel;Dept. of Geology. The Hebrew University of Jerusalem, Jerusalem, Israel |
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| Abstract: | Small live individuals of Globigerinoides sacculifer which were cultured in the laboratory reached maturity and produced garnets. Fifty to ninety percent of their skeleton weight was deposited under controlled water temperature (14° to 30°C) and water isotopic composition, and a correction was made to account for the isotopic composition of the original skeleton using control groups.Comparison of. the actual growth temperatures with the calculated temperature based on paleotemperature equations for inorganic CaCO3 indicate that the foraminifera precipitate their CaCO3 in isotopic equilibrium. Comparison with equations developed for biogenic calcite give a similarly good fit. Linear regression with Craig's (1965) equation yields: where t is the actual growth temperature and Is the calculated paleotemperature. The intercept and the slope of this linear equation show that the familiar paleotemperature equation developed originally for mollusca carbonate, is equally applicable for the planktonic foraminifer G. sacculifer.Second order regression of the culture temperature and the delta difference (δ18Oc ? δ18Ow) yield a correlation coefficient of r = 0.95: and δ18Ow are the estimated temperature, the isotopic composition of the shell carbonate and the sea water respectively.A possible cause for nonequilibnum isotopic compositions reported earlier for living planktonic foraminifera is the improper combustion of the organic matter. |
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