Response of the pelagic environment to palaeoclimatic changes in the central Mediterranean Sea during the Late Quaternary

Three central Mediterranean deep-sea cores have been studied to reconstruct the palaeoclimatic history of the basin over the time interval 34-0 kyr BP . The intensity and duration of the climatic events that occurred in the Me diterranean Sea during the last glacial-postglacial transition were estimat ed by observing compositional changes in the planktonic foraminifera and ca lcareous nannoplankton (coccolithophores) assemblages, together with a reco nstruction of sea surface temperatures (using Modern Analogue Technique and U-37(k') index), the delta O-18 signal and pteropod fluxes. The applicatio n of two independent and well established techniques for the determination of the past SST led to a number of considerations about the accuracy and ef ficacy of the use of such methodologies in the Mediterranean Sea, notorious ly dominated by local factors and characterised by a number of independent environments. The recognition of millennial to centennial climatic instabil ities, in both the SST and microfossil records, was possible because of the high resolution of the study. A succession of nine main biozones and six s ubzones, based on the major changes in the planktonic foraminifera records, has been recognised and compared with GRIP and GISP2 ice cores delta O-18 values and with records from four other studies from the central Mediterran ean Sea. During the early phase of the Holocene, a period characterised by relatively higher temperatures and lighter delta O-18 values has been recog nised as being coeval with the 'Climatic Optimum' (between 10.5 and 6.1 kyr BP, calendar age). This interval was characterised by an abrupt drop in th e pteropods relative abundances and fluxes. The pteropodal fossil assemblag e may have been affected by a possible event of selective dissolution of th e aragonite driven by the shoaling of the ACD. A coeval change in the posit ion of the pycnocline may have been responsible for a strong relative incre ase in abundance of Neogloboquadrina pachyderma r.c., and a decrease in the abundance of Globorotalia inflata in the western sector of the Mediterrane an Sea. (C) 2001 Elsevier Science B.V. All rights reserved.