were accompanied by uplifted geanticlines, which then eroded, providing sediments that filled the geosynclinal basin. According to Stille, geosynclines were formed from crustal folding rather than faulting; if faults were present in geosynclines, they were the product of later processes, such as the final collapse of the geosyncline. Gustav Steinmann interpreted ophiolites using the geosyncline concept. He theorized that the apparent lack of ophiolite in the Peruvian Andes was indebted either to the Andes being preceded by a shallow geosyncline, or because the Andes represented just the margin of a geosyncline. Steinmann contributed this correlation to the distinction between Cordilleran and Alpine-type mountains. According to Stille, a type of geosyncline called a "eugeosyncline" was characterized by producing an "initial magmatism", which in some cases corresponded to ophiolitic magmatism. With respect to oceanic basins, Kober held them to be separate and distinct from geosynclines. He nonetheless believed that mid-ocean ridges were orogens, although Stille disagreed, asserting that they were places of extensional tectonics, as exemplified by Iceland. Meanwhile, Argand argued that geosynclines, sufficiently attenuated through stretching, could become oceans basins, as a material called "sima" surfaced. See also References Bibliography King, Philip B. (1977) The Evolution of North America, Revised edition, Princeton University Press, pp 54–58 Kay, Marshall (1951) North American Geosyncline: Geol. Soc. America Mem. 48, 143pp. External links Obsolete geology theories