THE DEMISE OF SVERDRUP BASIN - LATE CRETACEOUS PALEOGENE SEQUENCE STRATIGRAPHY AND FORWARD MODELING

Five third-order stratigraphic sequences comprising Upper Cretaceous-Paleogene successions on Ellesmere and Axel Heiberg islands (Kanguk Formation and Eureka Sound Group) record fundamental changes in the mechanisms of subsidence and the ultimate demise of Sverdrup Basin. Sequence 1 (Cenomanian-Maastrichtian) represents a continuation of typical Sverdrup sedimentation patterns (delta and associated facies), and long-lived, thermally controlled subsidence where sedimentation rates averaged 3 cm/ky. Relative fall of base level at the end of the Cretaceous resulted in a basinwide sub-Paleocene unconformity, below which some or all Maastrichtian strata were removed. This event coincided with changes in sea-floor spreading in Canada Basin and northern Labrador Sea, and rejuvenation of volcanism along the northern basin margin. Foredeep-like subsidence and sedimentation began in the Paleogene. Subsidence was caused by compression and crustal buckling associated with shortening between Greenland and Arctic North America rather than by tectonically emplaced vertical loads. Accordingly, Sequences 2 to 4 (Paleocene-Middle Eocene) record significant increases in subsidence and sedimentation rates in the ''preorogenic'' basin. Deposition in the preorogenic Sverdrup Basin culminated with Sequence 4 (Late Paleocene-Middle Eocene), the basin being filled to sea level. Basin size, and sedimentation rates that averaged 15 cm/ky but sometimes were as high as 20-40 cm/ky, were greatest during deposition of Sequences 3 and 4. Syntectonic conglomerate appears locally in Early Eocene fault-bounded basins (Sequence 4-Otto Fiord and Emma Fiord). Nevertheless, the preorogenic basin survived as a subsiding entity until Middle Eocene time, despite the local deformation. Increased shortening and crustal failure during Middle Eocene time eventually fragmented the Sverdrup Basin into narrow, syntectonic intermontane basins (Sequence 5), marking its demise.