Biostratigraphy and sequence stratigraphy of the Lower and Middle
详细信息      
摘要

Material from shallow cores drilled through the uplifted and truncated deposits near the Svalis Dome in the Barents Sea contains Lower and Middle Triassic palynomorphs and ammonoids. Eight miospore assemblage zones have been established in this paper, and six of them are calibrated by ammonoids: Svalis-1 is dated by ammonoids of the late Griesbachian commune Zone. The assemblage is recovered from the Havert Formation overlying the Permian limestone. Svalis-2 is dated by ammonoids to the late Smithian tardus Zone. The deposits belong to the lower and middle parts of Klappmyss Formation. The unit represents the transgressive systems tract of a Smithian-early Spathian T-R Sequence. Svalis-3 is recorded from the youngest part of Klappmyss Formation which is missing age conclusive faunal evidence. The palynological assemblage is correlated as early Spathian in age. The deposits represent the regressive systems tract of the Smithian-early Spathian T-R Sequence. Svalis-4 is recovered from rocks deposited above the lowest part of the Steinkobbe Formation. Ammonoids of the subrobustus Zone date the deposits to the late Spathian. The main part of the unit represents the transgressive systems tract of the Spathian T-R sequence. Svalis-5 is recovered from a thin interval representing the middle part of the Steinkobbe Formation. Ammonoids restricted to the arkhipovi and evolutus zones date the assemblage as early Anisian. The deposits represent the lowest part of the lower-middle Anisian transgressive systems tract. Svalis-6 is dated by ammonoids of the middle Anisian varium Zone. The assemblage is recovered from deposits representing the middle part of Steinkobbe Formation. The deposits comprise the upper part of a transgressive systems tract as well as the regressive systems tract of the lower-middle Anisian T-R sequence. Svalis-7 is dated by ammonoids related to the late Anisian laqueatus Zone. The assemblage is recovered from the youngest part of Steinkobbe Formation, a unit which is interpreted as comprising the upper Anisian T-R sequence and the Ladinian transgressive systems tract above it. Svalis-8 is recovered from deposits representing the middle part of Snadd Formation. The deposits are dated as Ladinian on the basis of palynological correlation. They represent the regressive systems tract of the Ladinian T-R sequence.

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