Mediterranean planktonic foraminiferal faunas during the last glacial cycle

This paper highlights the planktonic foraminiferal abundance variations during the last glacial cycle from six new cores along a roughly west–east transect in the Mediterranean Sea, together with results from previous studies. Multivariate statistical analysis describes a first significant axis that indicates a general sea surface temperature (SST) gradient from west to east. As expected lower SST values are recorded in glacial times but the eastern and western basins seem to have reacted differently to glacial conditions. The western basin shows a SST decrease from the Alboran Sea to the central Mediterranean, whereas the eastern basin records a west to east increase that is similar to the present-day eastern Mediterranean gradient. These new results show that: (1) few almost basin-wide faunal trends may be recognised, but these are interrupted by local anomalies with opposing trends; and (2) major abundance variations are distinctly diachronous in some species and virtually synchronous in others. The implication is that over the glacial–interglacial timescale concerned, biostratigraphy should only be used on a local rather than basin-wide scale, unless it is supported by other independent dating methods