Abstract

Magnetic anomalies in the North Atlantic have been analyzed by Pitman and Talwani to determine a sequence of finite difference poles of relative motion of North America with respect to Africa for the time period 180 m.y. B.P. to the present. A similar analysis of South Atlantic magnetic anomalies by the writer determines a sequence of finite difference rotations of South America with respect to Africa for the time period 127 m.y. B.P. to the present. The two sequences of finite difference rotations are used to calculate the relative motion of South America with respect to North America for late Mesozoic and Cenozoic time.

From Triassic to Early Cretaceous time, South America moved to the southeast away from North America. From Early Cretaceous to Late Cretaceous time, South America moved eastward with respect to North America. Southeastward motion of South America occurred again from Late Cretaceous to early Tertiary time followed by northward motion from early to late Tertiary. Tectonic styles in the Caribbean region change when major plate motions change; however, the details of Caribbean geology cannot be explained by simple plate margins between North and South America. Tertiary compressional structures on the northern and southern margins of the Caribbean can be attributed to Tertiary closure between North and South America, but earlier tectonic regimes are not so easily related directly to North America—South America motions.

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