PALEOCENE OCEANS AND CLIMATE - AN ISOTOPIC PERSPECTIVE

The early Cenozoic was a time of climatic and oceanographic transition from the Cretaceous ''Greenhouse'' world to the ''Icehouse'' world of the Neogene. delta(18)O measurements shed light on ocean temperature and possible polar ice fluctuations during this interval, while delta(13)C measurements monitor fluctuations in ocean productivity, deep water circulation and atmospheric CO2. The major features from delta(18)O analysis of the early Cenozoic are general cooling of surface waters, with some evidence for transient cooling across the K/T boundary. Surface water temperatures were at a Cenozoic maximum in the early Eocene, whereas deep waters cooled then warmed during the Palaeocene. The delta(13)C Of bulk carbonates is at a minimum at the start of the Cenozoic due to the profound crisis in ocean surface water productivity associated with the extinctions of marine plankton at the Cretaceous/Tertiary boundary, thereafter delta(13)C values increase (in bulk carbonates, as well as planktonic and benthonic foraminifera) to their Cenozoic maximum in the late Palaeocene (c. 60 Ma), after which time they again decrease over an interval of c. 4.5 m.y. to a Cenozoic low in the early Eocene. The increase in delta(13)C values characteristic of the Palaeocene period is probably related to a combination of increasing surface water productivity and accelerated burial of organic carbon, conversely the decline in delta(13)C into the early Eocene is probably related to a decrease in ocean productivity and a deceleration in the rate of organic carbon burial. Benthic delta(13)C comparisons suggest that deep waters appear to have been predominantly formed in the high southern latitudes with the exception of a short lived interval near the Palaeocene/Eocene boundary possibly associated with a transient climatic anomaly (The ''Late Palaeocene Thermal Maximum''). The thermal change of Palaeocene deep waters may be related to the changing productivity of surface waters by controlling atmospheric CO2 flux in a similar way to that proposed for the control of the Pleistocene glacial cycles.