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Grad student talk - The effects of dissolution on Mg/Ca ratios in planktic foraminifera

Thursday, March 09, 2017, 12:30PM - 1:30PM


Brigitta Rongstad



The planktic foraminifera Mg/Ca temperature proxy is a well-established tool for reconstructing past ocean temperatures; however, it is well documented that partial dissolution of planktic foraminiferal tests results in a reduction of Mg/Ca ratios. While traditional analysis techniques have made it difficult to both identify the exact mechanism through which Mg is lost and apply accurate dissolution corrections, individual foraminifera analyses (IFA) allows scientists to distinguish between the three models for Mg loss: (1) a percent loss of Mg in individuals; (2) a molar loss of Mg in individuals; and (3) a loss of the highest-Mg (warmest) individuals in a population. I will present results from a novel individual foraminifera Mg/Ca method to examine the effects of dissolution on Mg/Ca ratios in three species of planktic foraminifera, N. dutertrei, G. ruber, and P. obliquiloculata, from a depth transect of core tops on the Ontong Java Plateau. With the exception of the most heavily dissolved populations of N. dutertrei and P. obliquiloculata, our data best supports a percent Mg loss model as indicated by the preservation of inferred temperature distribution shape among the sampled populations. Coupled with estimates for foraminiferal test dissolution, identification of the percent Mg loss model will allow for more accurate dissolution corrections in Mg/Ca paleothermometry work.