Numerous errors have crept into previous ecstatic curves because they have relied on unstable reference frames such as passive margins. A stable frame of reference is found in the Russian platform and allows a eustatic curve to be constructed without the subsidence corrections needed for subsiding margins. The stability of the Russian platform is indicated by flat-lying Mesozoic-Cenozoic sedimentary strata that have remained undeformed and untilted since deposition. These strata are no thicker than 200 m throughout the Russian platform. Individual lithofacies are continuous over large distances, suggesting a very flat hypsometry in which facies types were particularly sensitive to changes in sea level. The tectonic stability of the Russian platform allows ecstatic curves to be constructed through two complementary methods. The first method, the results of which we present here, uses backstripping to calculate sea-level changes from stage to stage. The second method uses the elevation of former shoreline deposits to calculate the net sea-level change from a former sea level to present sea level. Preliminary results suggest an unsteady 110-m rise in sea level from Bajocian to Albian time.
- Geological Society of America