Abstract

Drs K. J. H & E. L. Winterer write: In a succinct account on the causes of world-wide changes in sea level, Donovan & Jones (1979) correctly pointed out the importance of relating the rate of eustatic changes to mechanisms. Whereas changes in the volume of ocean ridges may produce slow eustatic changes, of the order of 1 cm/1000 years, rapid regressions and transgressions, at the rate of 1 cm/year or so, could only be attributed to changes in the volume of land ice, or to desiccation of isolated ocean basins. They also indicated that glacio-eustatic changes could take place only when polar ice caps existed, but seemed puzzled by the sudden sea level changes during the Jurassic, Cretaceous, and much of the Tertiary.

Some years ago one of us (E.L.W.) came to a similar conclusion that rapid eustatic changes, taking place in a few thousand or tens of thousands of years, cannot be related to tectonic changes, but must be related to glaciation or to desiccation. Deep-sea drilling results indicated that glaciation in Antarctica started as long ago as early Tertiary, and that the change in sea level caused by growth of wasting of glaciers in that region could amount to c. 60 m (Berger & Winterer 1974, p. 28).

The effect of desiccation of isolated basins on sea level seemed also to have been underestimated by Donovan & Jones. Referring to the Messinian desiccation of the Mediterranean (Hsü et al. 1973), they suggested that the amount of sea

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