A comparison of Mg/Ca ratios in Globigerinoides ruber (white): sensu stricto versus a mixture of genotypes

Abstract

Mg/Ca ratios were measured in core AAS9/21 from the eastern Arabian Sea (EAS), on two sets of planktonic foraminifera, one with a mixture of Globigerinoides ruber genotypes (sensu stricto and sensu lato) and the second which contained only G. ruber sensu stricto, living in the top 30 m of the water column. During the Holocene, sea surface temperatures (SSTs) in set 1 are cooler in comparison to that of set 2. During the deglaciation, SSTs derived using both these sets are similar, probably due to increased upwelling during this period. The drawback in using undifferentiated G. ruber is that the relative proportion of each genotype varies through different time periods as seen in the EAS and may influence the temperature reconstructions