ABSTRACT
Temperature fluctuations over long time periods are reflected by the variation of the oxygen isotope composition ( 18O) of foraminifera preserved in deep-sea sediments (Box 3.2). Two cores have been published which reflect the 18O changes over the last half million years. TR171-24, located in 2,328m of water off south-west Crete covers approximately 500ka, back to Marine Isotope Stage (MIS) 13 (Thunell and Williams, 1983). MD 84641, at a depth of 1,375m between the Nile Delta and Cyprus, extends back to 461ka, in MIS 12 (Fontugne
1 Eccentricity is the extent to which the orbital path of the Earth varies from being almost circular, to becoming increasingly elliptical due to the gravitational effects of the Sun, the Moon and the other planets. The dominant periodicities of the eccentricity are around 100 and 400ka, but much longer cycles also exist.
