Sea-level fluctuations due to changing mid-ocean ridge volumes have been calculated for the last 80 m.y. in 5-m.y. intervals. An analysis of the errors involved in this set of calculations includes: the effect of omitting calculations for crust more than 70-m.y. older than the ridge crest at any given time; inaccurate estimates of stage poles and ridge lengths; subducted ridges for which only a remnant triple junction remains; completely subducted ridges; and uncertainty in absolute dating of magnetic anomalies. The maximum possible sea level 80 m.y. ago was 365 m (1,198 ft); the minimum was 45 m (148 ft) with a most probable height of about 230 m (755 ft) above present sea level. A decrease in spreading rates since the Late Cretaceous was the primary cause of a volume decrease in mid-ocean ridges.
Figures & Tables
The result of a session at the 1981 AAPG Annual Meeting, this volume attempts to document global age and magnitude of sea-level shifts, and ultimately, the cause of the short-term shifts. Twelve individual papers were published on topics such as: comparative anatomy of cratonic unconformities; relation of unconformities, tectonics, and sea-level change; outcrop features and origin of basin margin unconformities; significant unconformities and the hiatuses represented by them; regional unconformities and depositional cycles; relative sea-level changes during the Middle and Late Cretaceous; Late Oligocene-Pliocene transgressive-regressive cycles of sedimentation; oxygen-isotope record of ice-volume history; oceanic ridge volumes and sea-level change; Jurassic unconformities, chronostratigraphy, and sea-level changes; Cenozoic regional arosion of the Abyssal sea floor; and depositional sequences and stratigraphic gaps on submerged United States Atlantic margin.