The ^dgr¹⁸O values for shallow-dwelling planktonic foraminifers vary as a function of global ice volume and local temperature. By using only sites which have been shown to have had a stable sea surface temperature during late Pleistocene, we propose to constrain paleotemperature to near-constant modern values. For such sites, variation in ^dgr¹⁸O of shallow-dwelling planktonic foraminifers is thus constrained to reflect variation in global ice volume.

With regard to average values, we suggest the earth has had a significant ice budget since the Cenomanian (approximately 100 m.y. ago). Thus, variation in the average state of the global ice budget is a likely cause for interregional unconformities.

It is possible to evaluate the stability of continental ice caps by sampling short intervals of core in extreme detail. Our preliminary isotopic results show that high-frequency variation of ice volume persists throughout the last 40 m.y. at no less than 25% of the late Pleistocene amplitude. This implies that high-frequency sea level fluctuations of at least 30 m are superimposed upon longer term trends.

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