*3.6. Paleoceanographic Indices*

The planktonic foraminiferal relative distributions were used as a first-order estimate of sea-surface temperature (SST) variations. An index of the SST variations was constructed based on the down-core variation of planktonic foraminiferal abundances, referred to as planktonic paleoclimatic curve (PPC). The PPC was obtained by the formula 100 × (w − c)/(w + c), where w represents the warm-water indicators (*G. ruber*f. alba, *G. ruber*f. rosea, *Orbulina universa, G. sacculifer* gr., *Globoturborotalita rubescens*, and *G. siphonifera* gr.), and c the cold-water indicators (*Globorotalia inflata, Globorotalia truncatulinoides, Turborotalita quinqueloba, G. glutinata*, and *Globorotalia scitula*). The eutrophication index (E-index; [7]) was estimated using the sum of the eutrophic species (*N. pachyderma, N. dutertrei, G. bulloides, T. quinqueloba*, and *G. inflata*) versus the sum of the eutrophic plus oligotrophic species (*G. ruber* alba, *G. ruber* rosea, *G. rubescens, G. sacculifer, O. universa*, and *G. siphonifera*). The down-core ratio between *G. bulloides* and *G. ruber* was also estimated showing the degree of the stratification of the upper water column [86]. Following [7], this ratio is referred to as S-index, and its values reflect periods of strong summer stratification of the water column where oligotrophic taxa dominate (low values) and/or periods of strong winter mixing of the water column where eutrophic taxa dominate (high values).
