Oxygen Cenozoic records

Prentice M.L. and Matthews R.K. (1988) Cenozoic ice-volume history Development of a composite oxygen isotope record. Geology 16,963-966. 

Over the long term, the Cenozoic deep-sea oxygen isotope record is dominated by two important features that relate to major shifts in mean climatic state. The first is a rise in values from 53 to 35. This trend, which is mostly gradual but punctuated by several steps, is an expression of the Eocene transition from greenhouse to icehouse conditions. In the Early Eocene (—53 Ma) the deep sea was relatively warm, —7 °C warmer than present, and there were no ice sheets. Over the next 20 Myr. the ocean cools, and the first large ice sheets appear on Antarctica. The latter event is reflected by the relatively sharp l.2%o increase in 5 0 at 33.4 Ma. This pattern reverses... 

Shackleton N. J. (1987) The carbon isotope record of the Cenozoic history of organic carbon burial and of oxygen in the ocean and atmosphere. In Marine Petroleum Source Rocks Geological Society Special Publication 26 (eds. J. Brooks and A. J. Fleet). Blackwell, Boston, pp. 423-434. 

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