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

Five third-order stratigraphic sequences comprising Upper Cretaceous-P aleogene successions on Ellesmere and Axel Heiberg islands (Kanguk For mation and Eureka Sound Group) record fundamental changes in the mecha nisms of subsidence and the ultimate demise of Sverdrup Basin. Sequenc e 1 (Cenomanian-Maastrichtian) represents a continuation of typical Sv erdrup sedimentation patterns (delta and associated facies), and long- lived, thermally controlled subsidence where sedimentation rates avera ged 3 cm/ky. Relative fall of base level at the end of the Cretaceous resulted in a basinwide sub-Paleocene unconformity, below which some o r all Maastrichtian strata were removed. This event coincided with cha nges in sea-floor spreading in Canada Basin and northern Labrador Sea, and rejuvenation of volcanism along the northern basin margin. Forede ep-like subsidence and sedimentation began in the Paleogene. Subsidenc e was caused by compression and crustal buckling associated with short ening between Greenland and Arctic North America rather than by tecton ically emplaced vertical loads. Accordingly, Sequences 2 to 4 (Paleoce ne-Middle Eocene) record significant increases in subsidence and sedim entation rates in the ''preorogenic'' basin. Deposition in the preorog enic Sverdrup Basin culminated with Sequence 4 (Late Paleocene-Middle Eocene), the basin being filled to sea level. Basin size, and sediment ation 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. Syntecto nic 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 durin g Middle Eocene time eventually fragmented the Sverdrup Basin into nar row, syntectonic intermontane basins (Sequence 5), marking its demise.