Abstract

Twelve second- and third-order T-R (transgressive-regressive) sequence boundaries have been delineated in the Triassic succession of the Sverdrup Basin, Arctic Canada. Sequence stratigraphic data from six other localities throughout the world, including Svalbard and Barents Sea, Germany, Italy, eastern Siberia, northern Himalayas and the southwestern U.S.A. indicate that these boundaries are global in extent. The ages and orders of these global sequence boundaries are: 1) near Permian-Triassic boundary (2nd order), 2) late Dienerian (3rd order), 3) late Smithian (3rd order), 4) near Early-Middle Triassic boundary (2nd order), 5) late Anisian (3rd order), 6) near Middle-Late Triassic boundary (2nd order), 7) early Carnian (3rd order), 8) mid-Carnian (3rd order), 9) near Carnian-Norian boundary (2nd order), 10) mid-Norian (3rd order), 11) near Norian-Rhaetian boundary (2nd order), and 12) near Triassic-Jurassic boundary (2nd order). All twelve of these high-order boundaries are also readily recognizable in the Triassic succession of the Western Canada Sedimentary Basin. A widespread unconformity is associated with each boundary on the basin margin with a conformable transgressive surface forming the boundary farther basinward. Various potential stratigraphic traps are associated with each boundary. At various localities, the global sequence boundaries commonly exhibit the effects of tectonic uplift and thus tectonics was a factor in the generation of these boundaries. To accommodate the combination of both tectonic and eustatic mechanisms in the generation of the global boundaries, it is proposed that they are a consequence of episodic, major plate tectonic reorganizations. During these episodes, changes in spreading rates and/or directions would induce changes in the horizontal stress regimes of the oceanic and continental portions of plates. This would in turn result in an initial eustatic fall and tectonic uplifts along basin margins. During the subsequent relaxation phase, eustatic rise and tectonic subsidence on basin margins would occur. These combined eustatic and tectonic movements would create sequence boundaries consisting of subaerial unconformities and conformable transgression surfaces as well as associated stratigraphic surfaces including ravinements, maximum flooding surfaces and regressive surfaces of marine erosion within stratigraphic successions in many areas throughout the world.

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