Triassic Sequence Stratigraphy of the Southwestern Barents Sea

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Abstract
Regional studies of Triassic sequences on the southwestern Barents Shelf (20–32°E, 71–74°N) revealed units that correlate seismically for hundreds of kilometers. Seismic character analysis identifies three Lower-Middle Triassic units with a composite progradational pattern, indicating sediment supply from the southeast (Induan, Olenekian and Anisian time). Fluvial, deltaic and marine deposits are predicted and located relative to paleo-coastlines. Shallow-marine conditions with limited vertical aggradation prevailed during the Ladininan time. A major shift in basin configuration took place in early Carnian time, and during the Late Triassic Epoch, the main sediment supply was from uplifted areas to the northeast, leaving sequences of marine to fluvial sediments on a tilted basin margin. The predictions based on this seismic stratigraphic approach proved valuable when correlating and evaluating well information. Building a stratigraphic framework based on seismic stratigraphy, detailed analysis of well-logs and biostratigraphy combined with regional correlations in the Arctic basins led to the identification of a succession of five 2nd-order cycles, each consisting of several sequences. Second-order cycle boundaries seem to correspond to changes in the tectonic regime/lithospheric stress, affecting the regional basin configuration; 2nd-order cycles correspond to T/R (transgressive/regressive) cycles, whereas sequences may be classified as 3rd-order cycles. A number of the sequences defined in this paper may well be of eustatic origin.

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