INFLUENCE OF CHANGING OCEANOGRAPHY ON BRYOZOAN FAUNAS IN THE LATE PALEOZOIC OF THE SVERDRUP BASIN, CANADIAN ARCTIC ARCHIPELAGO

The Carboniferous to Permian succession in the Sverdrup Basin records a transition from warm- to cool-cold-water carbonates. The Late Carboniferous warm-water Nansen Fm shallow water carbonate facies are Photozooan associations of fusulinid and non-fusulinid foraminifera, algae, Tubiphytes, and ooids. Siliciclastic rich platform and slope facies are typified by brachiopods, bryozoans, echinoderms, foraminifera, including fusulinids, and algae. Bryozoan faunas are dominated by fenestellid taxa (Alternifenestella prominent), and include the cystoporate Ramipora, the cryptostome Timanodictya, and rare trepostomes.

The overlying unconformity bound Sakmarian-Artinskian sequence (Raanes and Great Bear Cape Fm) contains a mixed cool- and warm-water fauna (Bryonoderm extended). Bryozoans, brachiopods, and echinoderms are prominent as are fusulinids and other benthic foraminifera. Algae are absent, but sponge spicules are common. Bryozoans comprise diverse fenestellids, locally common cystoporates (Ramipora, Goniocladia), and rare cryptostomes Timanodictya and Permoheloclema.

The cool-water Roadian-Wordian sequence (Assistance-Lower Trold Fiord Fm) comprises a Bryonoderm assemblage, dominated by bryozoans, brachiopods and echinoderms, with common benthic foraminifera and sponge spicules. Bryozoan faunas are fenestellid rich, but cystoporates (Goniocladia, Ramipora) or branching trepostomes (Dyscritella, Stenopora) and cryptostomes (Permoheloclema) dominate individual beds. The Capitanian to Wuchiapingian (?) cool to cold-water glauconitic sandstone and chert sequence (Upper Trold Fiord Fm to Lindstrom Fm) contains similar faunal groups with numerous bryozoans and sponge spicules.

In the Sverdrup Basin warm-water realm, bryozoan faunas were localized to deep water environments. As the ocean cooled, and trophic resources rose, bryozoan diversity increased and they dominated shallow-water environments. Further decrease in ocean temperatures led to reduced bryozoan diversity, but increased relative abundance of specific taxa.