Alpine Geology and Geosynclines: Birth and Death of the Concept In a Small Mountain Range

The geosyncline is not a concept ‘made in America'. In 1828 Élie de Beaumont noticed in the Western Alps that their sedimentary sequences were thicker, more ‘pelagic' in character and more deformed than those equivalent sequences in extra-Alpine areas in Europe. He ascribed this to the formation of a synclinal basin before the Alps had originated. He thought that the basin would be more vulnerable to thermal contraction-driven streses and would eventually fail to create a mountin range. He and Dufrénoy later in 1848 corroborated this observation and noticed the same thing in the Pyrenees. They also thought that the Paris Basin was a present-day example of such a synclinal basin. In 1852 Élie de Beaumont added the North Caspian Depression to his list of active basins that might give rise to a mountain range in the future. His work was known both to James Hall and to James Dwight Dana who are commonly credited for creating the concept of a geosyncline. in 1875 Eduard Suess wrote that he could not understand Hall's concept. In 1909 he rejected the idea of geosynclines on actualistic grounds. However, the idea of geosynclins was much developed by Émile Haug, who created a detailed reconstruction of the evolution of the Alpine geosyncline. This was taken over and modified by Émile Argand in his classic 1916 paper introducing the idea of embryonic tectonics. However, by 1922 Argand repudiated the idea of geosynclines and showed that ocean basins, small or large, predate mountain building and they form by extension and eventual rupture of the sial. However, his thinking was coloured the influence of the geosyncline idea, because he interpreted geosynclines as narrow oceans or extensional troughs with unruptured sial.