Wisconsin roots of the modern revolution in structural geology
Conventional wisdom long held that all important intellectual diffusion was from Europe westward to North America until the 1940s, but two examples of a reverse flow of fundamental concepts of structural geology during the 1920s challenge that dogma. Those concepts were products of the renowned Wisconsin school of Precambrian geology, and their transplantation also involved Princeton University. The first example of Wisconsin export concerns the use of sedimentary structures for establishing the original top facing or way-up direction within complexly deformed strata. Although this technique was recognized in nineteenth century Ireland, that insight was ignored and lost. Only after its reintroduction to Great Britain from Wisconsin in the 1920s was its importance gradually recognized in Europe. The second example concerns the recognition that small-scale deformational structures visible in isolated outcrops reflect larger regional structures, which are commonly not directly observable. This fundamental inference also had its roots in Wisconsin, where Englishman Gilbert Wilson learned it in 1925–1926 and then taught it at the Imperial College in London. These two key concepts of small-scale structural analysis, coupled with the use of the stereonet and insights from experimental deformation of rocks, became the basis for a revolution in structural geology during the 1950s to 1970s. After the triumphs of four generations of Wisconsin faculty members, who were outstanding both as scientists and administrators, the Wisconsin school faltered until the waves of that revolution washed back upon American shores during the 1960s.