The early fits: Congruent Conjugate Coastlines

Like Wegener, Du Toit (1937) also used the apparent congruence of the eastern South American coastline with the western African coastline to derive his fit (Fig. 1), however his argument was not so confined. Du Toit gave a list of several key factors necessary for continental reassembly in conjunction with the similarity of opposed coastlines. These included physiographical, stratigraphical, tectonic, volcanic, palaeoclimatic, palaeontological and geodetic considerations.

Figure 1. Du Toit, 1937.

Du Toit, 1937.

Du Toit’s original proposed fit for South America and Africa (Du Toit, 1937) as reproduced by Pplates.

While Du Toit proposed a reconstruction of Gondwana and postulated break-up in the Jurassic with subsequent drift, he did so as evidence for the Continental Drift hypothesis. Du Toit’s best fit estimate for Africa and South America suggested a 250- to 350-km separation of the coastlines. He recognised that subsequent tectonic and erosional processes have influenced the fragments, and thus modified their outlines. He stated that the mismatch arrived at using the current coastlines of South America and Africa can be explained by land “lost after fracture and during drift by erosion and/or submergence, much of it perhaps going to form the continental shelves”. Du Toit argued that the use of the continental shelf as the edge of the continent is no better than the use of the coastline.