Oxygen isotope ratios in ocean plankton
Colder	Warmer
lower sea level	higher sea level
boreal species	tropical species
ice sheets growing	ice sheets decaying
Glacial -- or Ice ages	Interglacial periods

Mark B. Bush, Ecology of a Changing Planet (Englewood Cliffs, N.J.: Prentice Hall, 2000), pp. 360-379.

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