Subsidence of the Sverdrup Basin, Canadian Arctic Islands

Abstract

Sverdrup Basin subsidence is separated into three phases: late Paleozoic (330 to 225 m.y. B.P.), early Mesozoic (225 to 124 m.y. B.P.), and late Mesozoic (124 to 74 m.y. B.P.). Each phase begins with high subsidence rates that decrease exponentially with time. During periods of rapid basin subsidence, regions adjacent to the basin perimeter experience mild uplift that migrates inward toward the basin center over a 10- to 30-m.y. period. Most of the observed basin subsidence (at least 70 percent) probably results from lithospheric response to loading of an initial depression. For the late Paleozoic and most of the early Mesozoic phases, observed subsidence and peripheral uplift relations, together with the pattern of exponential decay constants determined from subsidence curves, are consistent with the loading response of a lithosphere modeled as a viscoelastic beam. Late Mesozoic subsidence, because of thermal and structural events within the basin, presents no clear picture of lithospheric loading response. Late Paleozoic subsidence may have been initiated by thermal contraction of the lithosphere, whereas early Mesozoic subsidence probably resulted from downdropping of a graben block beneath the basin and late Mesozoic subsidence from downdropping centered along an axis collinear with the north-trending Boothia Arch exposed to the south of Sverdrup Basin. Pronounced increases in subsidence rates, mafic intrusions, and cessation of north-derived sediment in Sverdrup Basin at the beginning of Mesozoic time suggest that the opening of the Amerasian Basin of the Arctic Ocean by rifting and sea-floor spreading may have begun in Early Triassic time.