Technical Comments: Sea Level History
Bilal U. Haq and his co-workers have completed an important update of the chronology of coastal onlap and eustatic fluctuations in Mesowic and Cenowic time. Seismic stratigraphic results are augmented in the new charts by outcrop and well-log studies to document an impressive total of 119 sea level cycles since the beginning of the Triassic. In addition, the Cretaceous results have been published officially for the first time. However, apart from distinguishing between relative changes of coastal onlap and eustasy, the methodology and assumptions are much the same as those used to construct the first version of the "sea level curve" in 1977. In a recent evaluation of the seismic stratigraphic record of sea level change, we drew attention to two problems in particular. 1) All of the observed depositional cycles are assumed by Haq et al. to be eustatic. 2) The global onlap chart, which forms the basis for the smoothed eustatic curve, has little physical meaning.
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