Abstract

The Mesozoic succession of the Sverdrup Basin, Arctic Canada, is up to 9000 m thick and is characterized by repetitive third-order depositional sequences. Each sequence is tens to hundreds of metres thick and represents a time span of four to eight million years. Subaerial unconformities or ravinements bound the sequences on the basin margins whereas conformities or submarine unconformities form the boundaries in more central portions of the basin. A typical sequence consists of a thin, basal transgressive unit overlain by a thick regressive succession.

The sequences are the product of the interplay of the rates of seven main variables: 1) thermal subsidence, 2) compaction, 3) load subsidence, 4) mechanical subsidence or uplift due to changes in horizontal lithospheric stresses, 5) sediment supply, 6) glacio-eustacy, and 7) tectono-eustacy. The occurrence of marked changes in sedimentary regimes, source areas and patterns of uplift across many sequence boundaries indicates that tectonics played a pivotal role in the origin of the sequences. Thus, it is our interpretation that mechanical subsidence or uplift due to changes in horizontal lithospheric stresses (“Cloetingh Tectonic Model”) is the forcing function for third-order cyclicity. This model also accounts for the intercontinental extent of many sequence boundaries and the large differences in the magnitude of relative sea-level falls recorded in various basins.