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The Upper Triassic-Lower Jurassic Heiberg Deltaic Complex of the Sverdrup Basin
In early Norian large river systems began transporting vast amounts of sediment northward across the Precambrian Shield to the Sverdrup Basin. Two deltaic centres were established in the eastern and central Sverdrup and a highly constructive deltaic complex prograded northwestward from Norian until early Pliensbachian. Much of the basin was filled to sea level and the resulting vertical succession, which in places exceeds 3000 m, consists of prodelta shale and siltstone (Barrow Formation), delta front and tidal flat sandstone, siltstone and shale (Romulus Member, Heiberg Formation) and delta plain sandstone, siltstone, shale and coal (Fosheim Member, Heiberg Formation).
Two marine shale units penetrate the deltaic wedge in the west and three cycles of deltaic progradation are recognisable in the west-central Sverdrup (Barrow-Skybattle formations; Grosvenor Island-Maclean Strait formations; Lougheed Island-King Christian formations). These cycles reflect eustatic sea level changes and notable sea level rises occurred in early Norian, early Hettangian and early Sinemurian.
Farther west, a marine shelf was present lateral to the deltaic complex. Beach and tidal flat sandstones occur along the southern margin of the shelf. The sandstone units are truncated southward by unconformities and change facies to marine shale and siltstone to the north.
In late Pliensbachian sediment supply to the Sverdrup Basin was greatly reduced and a widespread sand sheet of destructive delta origin (Remus Member, Heiberg Formation) was deposited as the deltaic plain was gradually transgressed. Mud and silt of offshore shelf origin (Jameson Bay Formation) were deposited in the western Sverdrup at this time. In early Toarcian the destructive delta was drowned by a eustatic sea level rise and much of the Sverdrup was transformed into an offshore marine shelf.
Salt of the deeply-buried, Pennsylvanian Otto Fiord Formation was mobile during deposition of Norian-Pliensbachian strata. Salt-cored structures grew by hundreds of metres as deltaic sediments prograded toward and over them.
Norian to Pliensbachian sandstones of channel, delta front, beach and nearshore origin are reservoir strata in twelve hydrocarbon fields in the western Sverdrup. This area has a very favourable combination of reservoirs, hydrocarbon source rocks, traps and migration paths and will likely be the site of many more discoveries.
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