Abstract

Jurassic-Cretaceous rifting within Arctic North America that eventually resulted in the formation of the Amerasia Basin greatly affected deposition within nearshore terrestrial basins in surrounding areas, such as the Brooks-Mackenzie Basin and the Sverdrup Basin. In this paper, four measured stratigraphic sections and detrital U-Pb zircon data (N = 14; n = 3339) from outcrops within the Northern Richardson Mountains are integrated with well-log and core data from the adjacent Mackenzie Delta to establish a model-independent sequence stratigraphic framework for the Brooks-Mackenzie Basin. This framework is used to elucidate the underlying tectonic forces responsible for the observed stratigraphy, relating patterns of deposition to various phases of rift development. The proposed interpretation classifies the sub-Jurassic unconformity as a firstorder sequence boundary, demarcating a change in tectonic setting from pre-rift to rift, meaning it is also classified as the rift onset unconformity for the Amerasia Basin. The overlying Bug Creek Group is largely progradational, representing a first-order lowstand systems tract corresponding to early syn-rift strata. Detrital zircon data from the Bug Creek Group lacks syn-depositional detrital zircon and resembles the underlying Permian, suggesting a recycled source of sediment. A change in the detrital zircon signature is observed within the uppermost Aklavik Formation, representing a new source. This also coincides with a rapid transition from shoreface sandstones of the Aklavik Formation to the lower offshore deposits of the Husky Formation caused by normal faulting in the Husky Lakes Fault Zone which is associated with a dramatic basin expansion. Maximum transgression occurs above the Arenaceous Member of the Husky Formation, likely near the Jurassic-Cretaceous boundary, representing a first-order maximum flooding surface and rift-climax. Above the maximum flooding surface, the overall progradational signature represents a first-order highstand systems tract and early post-rift deposits. The sub-Hauterivian basal Kamik unconformity is observed at the base of the subsequent falling stage systems tract. This first-order sequence boundary is approximately time equivalent to the breakup unconformity for the Arctic Ocean, with the overlying Kamik Formation resembling the Isachsen Formation in the Sverdrup Basin.