SEA LEVEL STUDIES | Eustatic Sea-Level Changes, Glacial-Interglacial Cycles

The Quaternary has repeatedly witnessed major changes in eustatic sea level resulting from fluctuating ice volumes in response to insolation changes registered at the surface of the Earth. In the most general sense, the timing and magnitude of these eustatic changes have tended to conform to a consistent pattern in space and time as indirectly indicated oxygen isotope records from marine and ice cores, and corroborated by geomorphological and stratigraphical evidence. At a broad scale, since at least the start of the middle Pleistocene, glacioeustatic 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 close to 100 ka. Seven glacial cycles have occurred since the start of the middle Pleistocene some 780 ka ago. Glacial cycles of the early Pleistocene involved lower amplitude sea-level fluctuations and over shorter periods (40 ka cycles).