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 wat er 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. Sur face water temperatures were at a Cenozoic maximum in the early Eocene , whereas deep waters cooled then warmed during the Palaeocene. The de lta(13)C Of bulk carbonates is at a minimum at the start of the Cenozo ic due to the profound crisis in ocean surface water productivity asso ciated with the extinctions of marine plankton at the Cretaceous/Terti ary boundary, thereafter delta(13)C values increase (in bulk carbonate s, as well as planktonic and benthonic foraminifera) to their Cenozoic maximum in the late Palaeocene (c. 60 Ma), after which time they agai n decrease over an interval of c. 4.5 m.y. to a Cenozoic low in the ea rly Eocene. The increase in delta(13)C values characteristic of the Pa laeocene period is probably related to a combination of increasing sur face water productivity and accelerated burial of organic carbon, conv ersely the decline in delta(13)C into the early Eocene is probably rel ated to a decrease in ocean productivity and a deceleration in the rat e of organic carbon burial. Benthic delta(13)C comparisons suggest tha t deep waters appear to have been predominantly formed in the high sou thern latitudes with the exception of a short lived interval near the Palaeocene/Eocene boundary possibly associated with a transient climat ic anomaly (The ''Late Palaeocene Thermal Maximum''). The thermal chan ge of Palaeocene deep waters may be related to the changing productivi ty of surface waters by controlling atmospheric CO2 flux in a similar way to that proposed for the control of the Pleistocene glacial cycles .