EDUARD SUESS, EUSTATIC MOVEMENTS, AND GLOBAL BIOSTRATIGRAPHIC CORRELATIONS

The proposal by Wallace and Darwin of their joint theory of natural selection in 1857 led to a major dilemma for geologists: on the one hand, most agreed with Lyell that the geological record of the past is best interpreted in terms of processes now active, but on the other, also with Cuvier that the fossil record contained so many abrupt and global changes that it could be used to subdivide the geological history into systems and erathems. However, Lyell's world consisted of local processes taking place in a haphazard fashion on the surface of the globe making any global synchroneity impossible, whereas Cuvier's world was based on the assumption of widespread, almost global, catastrophes taking place at intervals which enabled a record of globally synchronous events. The irreconcilability of these two world views constituted the dilemma and it was not obvious how one could resolve it. Darwin, in The Origin of Species, chose to assume that the geological record was so incomplete as to create an illusion of abruptness of the changes in the fossil record. However, by the eighties of the nineteenth century, work on the fossil faunas, especially in the Cainozoic sequences in the mountain belts and basins around the Mediterranean had shown that many of the abrupt changes were real and required a different explanation from Darwin's. Eduard Suess demonstrated the synchroneity of many of the sea-level changes in 1880 and coined the term eustatic motions in 1888. Suess also showed that the major faunal transitions were associated with the most widespread regressions and claimed that they were caused by the episodic, contraction-driven subsidence of the ocean floors. He thus explained why global bio- and sequence stratigraphy worked so well. Suess' attempt to reconcile the world of Lyell and the world of Cuvier was what pushed him into tectonics and he discovered that it was the world of tectonics in the ocean basins that dominated the stratigraphic record and the history of life. Since then this discovery has been credited to many others, including Thomas Chrowder Chamberlin, but Suess' model was far more sophisticated than any of his imitators. Eventually his contractional model was proven wrong, but his intuition that the major regressions and transgressions were eustatic in nature and that their main cause was in the oceans basins remained correct.