Life and death of a Cambrian–Ordovician basin: An Andean three-act play featuring Gondwana and the Arequipa-Antofalla terrane
Sven O. Egenhoff, 2007. "Life and death of a Cambrian–Ordovician basin: An Andean three-act play featuring Gondwana and the Arequipa-Antofalla terrane", The Evolution of the Rheic Ocean: From Avalonian-Cadomian Active Margin to Alleghenian-Variscan Collision, Ulf Linnemann, R. Damian Nance, Petr Kraft, Gernold Zulauf
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Reconstruction of the facies architecture and geometries of the Cambrian–Ordovician succession in the Central Andes of southern Bolivia and northwestern Argentina reveals a tripartite basin history that closely corresponds to interpretations of regional plate tectonic movements. The analysis of basin deposits enabled tracing and timing of movements of the Arequipa-Antofalla terrane, which initiated, fed, and terminated a basin between the terrane and Gondwana during the early Paleozoic. Tectonic movements started in the Cambrian and led to the formation of an extensional basin. Stretching was more pronounced in southern Bolivia than in northwestern Argentina, resulting in widening of the basin to the north. This was produced by a counterclockwise rotation of the Arequipa-Antofalla terrane relative to Gondwana, with a Euler pole in northwest Argentina. Tectonic movements reversed in the late Early Ordovician (Expansograptus holmi biozone), with the terrane rotating clockwise back against Gondwana. Consequently, the extensional basin turned into a foreland trough, with its western part undergoing high subsidence. A forebulge developed on the eastern shelf, which triggered westward progradation of a delta, thereby significantly reducing basin width. Although compressional movements advanced from west to east, reliable bio-stratigraphic calibration was established only for facies on the distal part of the overridden plate as graptolite ecology and abundance in this area enhanced biostratigraphic resolution. In the Late Ordovician, the basin closed in northwestern Argentina but continued to accumulate coarse-grained, partially glacigenic debris in southern Bolivia.