(Table 2) Stable isotope analysis of Nuttallides truempyi and Rugoglobigerina rugosa from DSDP Site 62-463

Strong climatic and temperature fluctuations mark the Late Campanian and Maastrichtian as indicated by stable isotope records from the equatorial Pacific (Site 463) and middle and high latitude South Atlantic (Sites 525, 689 and 690). The first major global cooling decreased intermediate water temperatures (IWT) by 5-6°C between 73-70 Ma. At the same time, sea surface temperature (SST) decreased by 4-5°C in middle and high latitudes. Intermediate waters (IW) temporarily warmed by 2°C in low and middle latitudes between 70-68.5 Ma. Global cooling resumed between 68.5-65.5 Ma when IWT decreased by 3-4°C and SST by 5°C in middle latitudes. About 450 ka before the Cretaceous-Tertiary boundary rapid global warming increased IWT and SST by 3-4°C, though SST in the tropics changed little. During the last 200 ka of the Maastrichtian, climate cooled rapidly with IWT and SST decreasing by 2-3°C. During the global cooling at 71-70 Ma and possibly at 67-65.5 Ma, the sources of cold intermediate waters in the equatorial Pacific, Indo-Pacific and South Atlantic were derived from the high latitude North Pacific. In contrast, during the global climate warming between 65.2-65.4 Ma, the middle latitude South Atlantic was closest to the source of IW production and implies that the low latitude Tethys played a major role in global climate change. Climate changes, sea-level fluctuations and associated restricted seaways appear to be the most likely mechanisms for the alternating sources of IW production.

Late Cretaceous and Cainozoic bathyal Ostracoda of DSDP Site 62-463 in the Central Pacific (Fig. 3)

Cainozoic deep-sea ostracod assemblages from the summits of Mid-Pacific guyots point to high levels of endemism possibly as a result of their bathymetric separation from the surrounding sea floor. However, the interpretation of these fossil assemblages is hampered by the paucity of comparative material from surrounding non-guyot sites. Fifteen ostracod assemblages from DSDP Site 463 (Late Cretaceous-Pleistocene) were studied to compare with those from nearby guyots. Three distinct faunal assemblages are recognised at Site 463: Assemblage A (Maastrichtian-Eocene), Assemblage B (Oligocene-Upper Miocene) and Assemblage C (Upper Miocene-Pleistocene) although the palaeoenvironmental significance of these units is unclear. Sixty-two ostracod species are identified, the thirteen most abundant are discussed in the taxonomic section, five of which are described as new. Between 30 and 100% of the species encountered in each sample are considered as endemic to Site 463, while some of the remaining species were previously thought to be endemic to individual guyots. Similarly high levels of endemism on nearby guyots probably reflect an incomplete knowledge of deep-sea ostracod faunas rather than the establishment of geographically or bathymetrically restricted populations. The presence of globally pandemic and geographically widespread taxa on sites such as the Mid-Pacific Mountains, surrounded by abyssal depths which lie below the CCD, indicates that some faunal exchange or migration of ostracods does take place. This must be achieved within the intermediate waters and probably occurs passively.