The Atlantic Jigsaw Puzzle and the geoheritage of Angola

The jigsaw-puzzle fit of South America and Africa is an icon of plate tectonics and continental drift. Fieldwork in Angola since 2002 allows the correlation of onshore outcrops and offshore geophysical and well-core data in the context of rift, sag, salt, and post-salt drift phases of the opening of the central South Atlantic. These outcrops, ranging in age from >130 Ma to <71 Ma, record Early Cretaceous outpouring of the Etendeka–Paraná Large Igneous Province (Bero Volcanic Complex) and rifting, followed by continental carbonate and siliciclastic deposition (Tumbalunda Formation) during the sagging of the nascent central South Atlantic basin. By the Aptian, evaporation of sea water resulted in thick salt deposits (Bambata Formation), terminated by seafloor spreading. The Equatorial Atlantic Gateway began opening by the early Late Cretaceous (100 Ma) and allowed flow of currents between the North and South Atlantic, creating environmental conditions that heralded the introduction of marine reptiles. These dramatic outcrops are a unique element of geoheritage because they arguably comprise the most complete terrestrially exposed geological record of the puzzle-like icon of continental drift. The purpose of this contribution is to emphasize a well-known observation realized by authors even before Wegener (1966): the puzzle-like fit of the western coast of Africa with the eastern coast of South America. Our approach is to view the southern coast of Angola (Figs 1 & 2) as a unique region of geoheritage due to its remarkable documentation of the major phases of opening and growth of the central South Atlantic Ocean, defined originally by marine geophysical models and well-core analysis (Fig. 2). To our knowledge, the Angolan coast is the only place that preserves relatively easily visited onshore outcrops that reflect this geologically significant chapter in Earth history. J. Tuzo Wilson (1963) popularized plate tectonics by using the descriptive and easily visualized term ‘jigsaw-puzzle fit’ to describe the Atlantic coasts of Africa and South America (Fig. 2). Angola is at the centre of this jigsaw puzzle, and the geology of Namibe Province in southern Angola has geohistorical and geoheritage significance. The study of geology and of fossils in Angola has been reinvigorated in recent years, following the end of the civil war. Fossils are portable elements of geoheritage, and therefore worthy of perpetual care, so we include them here for their evolutionary, environmental, ecological, and palaeobiogeographical geoheritage value as it relates to the opening of the South Atlantic.

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