The geometry of continental displacement and its application to Arctic geology: Eugen Wegmann’s early approaches published in the Geologische Rundschau in 1943

Abstract

Plate tectonics developed around 1965 as a powerful tool to describe the tectonic movements of the Earth's crust. The article demonstrates that basically four already existing theoretical concepts-subduction, seafloor spreading, the application of Euler's theorem and transform faults-had to be combined to arrive at the modern theory. Alfred Wegener, father of the theory of continental displacement, is often credited as the most direct forerunner of plate tectonics. However, none of the aforementioned concepts had been developed by him. The present article deals with the hitherto not duly credited contributions of the Swiss geologist Eugen Wegmann (1896-1982). He developed in a series of highly original papers published between 1943 and 1948 (one of them in the Geologische Rundschau), a critical test of the theory of continental displacement based on the regional geology of the Arctic. Furthermore, he gave a very concise account on the geometrical principles of drift movements. As a result, he developed for the first time-25 years before McKenzie and Parker's landmark paper on the Pacific (1967)-the geometrical basis to graphically test plate motion directions. However, his work has not yet received the credit it deserves, neither by scientist nor by historians of science.

A pioneer of Precambrian geology: Boris Choubert’s fit of the continents across the Atlantic (1935) and his insights into the Proterozoic tectonic structure of the West African Craton and adjacent areas

“…Contrary to the situation in the German, the Anglo-Saxon (including the then still existing British Empire and associated countries), or the Dutch and Scandinavian world (Carozzi, 1985; Le Grand, 1988;Frankel, 2012a), the reception of Wegener's (1912Wegener's ( , 1915 hypothesis of continental displacement is not so well documented in the French world. The situation in the French-speaking part of Switzerland, where Argand's (1924) brilliant continental-scale mobilist tectonic analysis of Asia convinced several other workers to seriously consider continental displacement, is a notable exception and it has been discussed in detail in the literature (Şengör, 1982;Trümpy, 2001;Schaer, 2010Schaer, , 2011Frankel, 2012a;Letsch, 2013).…”

“…the Baltic shield) well into the 1960s and even later until the advent of trustworthy geochronological methods and the fast development of Precambrian (that is Proterozoic) paleontology and biostratigraphy in the 1970s and 1980s (Schopf, 1992). Consequently, only very few of Wegener's contemporaries and even less of his sympathizers had firsthand knowledge of the Precambrian, with Eugene Wegmann (1935, see also Letsch, 2013) being an outstanding exception. Second, even after the triumph of tectonic mobilism in its reincarnation as new global or plate tectonics (Frankel, 2012d) during the 1960s, many geologists (with some notable exceptions, e.g.…”

R.A. Daly’s early model of seafloor generation 40 years before the Vine–Matthews hypothesis: an outstanding theoretical achievement inspired by field work on St. Helena in 1921–1922

“…Other proponents of a certain mobility of the continents, as, e.g., Joly (1923), Ampferer (1925), van Waterschoot van der Gracht (1928), or von Bubnoff (1931, expressed similar views. Hence, Wegener's version of continental displacement did neither imply any kind of production of new oceanic crust at the trailing edge of a continental block, nor any destruction (subduction) of oceanic crust at its leading edge (Letsch 2013). In fact, Wegener (1912Wegener ( , 1915Wegener ( , 1929 suspected that basaltic magmatism will accompany the denudation of sima behind a moving continent (as, e.g., beneath the Atlantic, see also Jacoby 1981).…”

“…And even some prominent historians of science have failed to appreciate this difference (e.g., Oreskes 1999, pp. 77-78) and thereby misinterpreted Wegener's figures and texts (see Letsch 2013). However, Wegener's assumption of the "sima sea" without a real geologic record was probably one of the main aspects of opposition against Wegener's theory of continental displacement.…”

“…Nevertheless, several peculiar concepts or techniques which later formed the very base of plate tectonics can be found -albeit in often somewhat different contexts -in some of these early mobilist writings. A particularly intriguing example is Wegmann's (1943) early use of a Mercator projection to document relative motions of crustal blocks (see Frankel 2012a andLetsch 2013) thereby anticipating the later seminal work of McKenzie and Parker (1967) on the Pacific plate.…”