Eustatic Sea-Level Changes, Glacial-Interglacial Cycles

Abstract

The Quaternary has witnessed repeated major changes in eustatic sea level resulting from fluctuating ice volumes in response to insolation changes registered at the surface of the Earth. The timing and magnitude of these eustatic changes have tended to conform to a consistent pattern, as indirectly indicated by the marine oxygen isotope record and corroborated by geomorphological and stratigraphical evidence. At a broad scale since at least the start of the middle Pleistocene, glacio-eustatic sea-level variations have occurred as part of glacial cycles. These cycles have seen the slow and progressive buildup of continental ice sheets and concomitant sea level lowering by as much as 130–120 m over a time span of approximately 100 ka. Seven glacial cycles have occurred since the start of the middle Pleistocene approximately 780 ka ago. Glacial cycles of the early Pleistocene involved lower amplitude sea-level fluctuations and over shorter periods (40-ka cycles).