Transgressive–regressive (T–R) sequence analysis of the Jurassic succession of the Sverdrup Basin, Canadian Arctic Archipelago

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.

Geodynamic Significance of Stacking Lower Cambrian Sequences Units in the Western Anti-Atlas

“…The vertically transition in facies stacking from progradational to retrogradational patterns constitutes the main factor in the recognition of unconformity in outcrop within the transgressive-regressive cycles. These unconformities can be interpreted as a transgressive surfaces located, not at the top of the lowstand system tract as in transgressive-regressive sequences [17], [18] and [19], but at the top of the Highstand system tract as suggested by the lack of evidence of significant erosion and a falling sea level system tracts.…”

Stratigraphic Unconformities: Review of the Concept and Examples from the Middle-Upper Paleozoic

“…Disconformity-bounded packages of sedimentary rocks, called cycles, cyclites, cyclothems, allostratigraphic units, and most commonly sequences, remained in focus for many decades, generating an impressive development of concepts, terminology, and discussion on local vs. global controls of base or sea level fluctuations [1,2,[12][13][14][15][16][17][18][19][20][21][22][23][24]. It should be noted that sequence stratigraphy significantly expanded definition of sequences by including both disconformities and their correlative surfaces (conformities) in more complete basincentered sections [14].…”

“…Transgressive tide and wave abrasion of coasts, estuaries, and shoreface are able to modify the configuration of subaerial surfaces and any terrestrial sediment accumulated on it. The surfaces produced by such an abrasion are called ravinement surfaces [17,22,23]. The depth of transgressive erosion greatly varies depending on induration of the exposed sediment, on the wave and tide energy of a transgressing sea, and on the slope angle of the eroded sediments.…”

Ordered hierarchy versus scale invariance in sequence stratigraphy

“…T-R sequence stratigraphy subdivides stratigraphic successions into transgressive-regressive couplets with the sequence boundary at the top of the regressive systems tract (Embry and Johannessen 1992;Embry 1993;Catuneanu 2006). The concept builds on the fact that most shallow-water deposits can be subdivided into shoaling and deepening intervals, frequently corresponding to intervals of increasing and decreasing influence from land in deepwater deposits.…”

“…This principle holds for a wide range of scales in time and space and could serve as the basis of a scale-invariant model of stratigraphic sequences. A hierarchy of cycles has been proposed for T-R sequences (Embry 1993;Catuneanu 2006, p. 331). Sequence ranks are distinguished by the range of base-level fall and the degree of change in sedimentary regime at the R/T sequence boundaries as well as by the degree of deformation that occurred during the formation of the boundary hiatus.…”