Abstract

Transgressive–regressive (T–R) sequence analysis has been applied to the Jurassic succession of the Sverdrup Basin with sequence boundaries drawn at subaerial unconformities or the correlative transgressive surfaces. A hierarchal system of sequence order that reflects the different nature of the boundaries has been formulated on the basis of boundary characteristics. Second- through fifth-order sequences have been recognized in the Jurassic succession, which itself is part of a first-order sequence of mid-Permian – Early Cretaceous age.The Jurassic strata occur within four second-order sequences. The boundaries of these sequences are characterized by widespread subaerial unconformities across which major changes in depositional and subsidence regimes occur. These boundaries are earliest Rhaetian, earliest Pliensbachian, earliest Bajocian, earliest Oxfordian, and Hauterivian in age.Each second-order sequence is divisible into a number of third-order sequences bounded mainly by basin-wide transgressive surfaces with subaerial unconformities present on the basin margins. The ages of the 10 Jurassic third-order sequences are Rhaetian – Hettangian, Sinemurian, Pliensbachian – Toarcian, late Toarcian – Aalenian, Bajocian, Bathonian, Callovian, Oxfordian – early Kimmeridgian, late Kimmeridgian – early Tithonian, and late Tithonian. The third-order sequences commonly contain three to six fourth-order sequences. These sequences are bound entirely by transgressive surfaces that can be correlated only over a portion of the basin.A good correlation between the second- and third-order transgressive events of the Sverdrup Basin and proposed global events is observed. This worldwide occurrence suggests that the events in part reflect eustatic sea-level changes. The characteristics of the second- and third-order boundaries also indicate that each had a tectonic influence that resulted in a rapid relative sea-level fall (uplift) followed by a rapid rise (subsidence). Given the apparent combination of tectonic and eustatic influence on the generation of the second- and third-order sequence boundaries, they are interpreted to reflect significant plate-tectonic reorganizations that affected the intraplate stress regimes of the oceanic (eustatic) and continental (tectonic) portions of each lithospheric plate.

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