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Abstract

Cratonic basins appear to occupy a specific place in the Wilson cycle, initiating after continental collision and supercontinent development, but before rifting and continental break-up. They do not result directly from the horizontal plate motions characteristic of the Wilson cycle, but from localized, long-lived subsidence. Covering c. 10% of the Earth's continental crust, most of the preserved cratonic basins developed in the Early Paleozoic after the formation of Gondwana and Laurentia. Recent investigation of the Parnaíba cratonic basin of Brazil has shown that this basin, and potentially cratonic basins in general, are characterized by six features: (1) formation on thickened lithosphere (>150 km); (2) a pronounced basal unconformity; (3) a sub-circular outline and large area of 0.5 × 105 to 2 × 106 km2; (4) long-lived (100–300 myr) quasi-exponential tectonic subsidence of shallow marine and terrestrial sediments; (5) no major extensional strain features, such as rifts, crustal or lithospheric thinning or Moho elevation; and (6) dense, high velocity and conductive lower crust and upper mantle. These characteristics indicate basin initiation and development by purely vertical subsidence of the lithosphere, either thermally or mechanically driven. Thermal subsidence may be related to orogenic thickening, radiogenic heating and erosion associated with supercontinent assembly, whereas mechanical subsidence may be a result of the emplacement in the lower crust or upper mantle of a dense igneous body related to plume activity during the lifetime of a supercontinent.

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