Evolution of Sverdrup Basin, Arctic Canada

Sverdrup basin, a structural depression near the northern margin of the North American craton, contains a succession up to 13,000 m thick of Lower Carboniferous to Tertiary, marine and nonmarine sedimentary rocks, basalt flows, and gabbro dikes and sills. The basin evolved in five phases: (1) late Paleozoic, when evaporites and marine muds were deposited in the axial region and carbonates and mature sands on the margins; (2) early Mesozoic, when great thicknesses of siltstone and shale accumulated in axial parts of the basin; (3) middle Mesozoic, when terrigenous clastic deposits accumulated slowly; (4) late Mesozoic, when clastic deposits widely overstepped former basin margins; and (5) late Mesozoic-Cenozoic, when the basin underwent three stages of tectonism (Eurekan orogeny). Some evaporite diapirs in the basin developed halokinetically, beginning probably in the early Mesozoic; others were generated during Tertiary folding and faulting. Mafic volcanism and intrusion occurred episodically at times of basin foundering. Depending on the availability of imported terrigenous detritus, phases of mafic activity (and foundering) were accompanied by widespread marine transgression or by vigorous basin filling. The thick sedimentary fill masks the fundamental character of the basin. If acutely starved depositional conditions had prevailed through its Paleozoic and Mesozoic history, Sverdrup basin in the latest Cretaceous would have been a small ocean basin with steep sides, a basaltic floor about 3,500 m deep, and a thin succession of deep marine sediments--fundamental attributes of some modern small ocean basins.