Abstract

The Sverdrup Basin is a pericratonic sedimentary trough in northern Canada containing up to 13 km of Carboniferous to Tertiary strata. The basin formed by late Paleozoic continental rifting and was subsequently affected by a series of alternating tectonic settings. Evaporite diapirs are well exposed at the present erosion level and occur mainly along the basin axis. The diapiric source layer consists of about 400 m of anhydrite underlain by salt of unknown stratigraphic thickness, deposited during the initial Permo-Carboniferous synrift phase of basin subsidence. Large salt–anhydrite diapirs rose into the sedimentary overburden when the overburden had reached a thickness of several kilometres. They grew during a relatively long period of modest horizontal compression from the Permo-Triassic to Early Cretaceous. Much smaller, tabular anhydrite diapirs were rapidly emplaced during periods of high horizontal compression, in the middle Cretaceous, when large flexural stresses were induced by sedimentary loading, and during the early Tertiary when high intraplate compression resulted from far-field tectonic forces during the Eurekan orogeny.The diapiric behaviour of dense anhydrite implies that buoyancy alone was incapable of driving the diapirism in the Sverdrup Basin. The importance of other driving forces, such as differential loading, basement or overburden faulting, extension, and thermal convection, is thought to be secondary. This suggests a correlation between diapirism and periods of significant horizontal compression, implying that plate-tectonic forces and flexural loading are important driving mechanisms of evaporite diapirism in the Sverdrup Basin.

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