Permian warm- to very cold-water carbonates and cherts in northwest Pangea

A vast area of northwest Pangea, extending from the Sverdrup Basin (Canadian Arctic) to the Barents Sea (Norwegian and Russian Arctic) was affected by a significant climatic cooling in Permian time. Warm tropical-like conditions prevailed during the Asselian and Sakmarian interval, cool to cold temperate-like conditions occurred during the Artinskian to Kazanian interval, and very cold polar-like conditions were established during latest Permian time (undetermined Kazanian-Tatarian). This climatic deterioration led to a significant shift in the composition of biogenic sediments. Asselian and Sakmarian shallow-water carbonates comprise abundant aragonite-secreted skeletal and non-skeletal elements (ooid, cement) dominated by abundant green algae and foraminifers, associated with a great variety of microfloral and invertebrate elements (Chloroforam Assemblage). These elements combine to form high- to low-energy facies including various buildups that range from small patch reefs to barrier-like structures extending for tens of kilometers. Submarine cements formed widely in both reefal and non-reefal carbonates. Evidence of meteoric-pedogenic diagenesis is pervasive in subaerially exposed carbonates. Artinskian to Kazanian shallow-water carbonates, which are poorly- to non-cemented by submarine phases, are dominated by bryozoans, echinoderms and brachiopods (Bryonoderm assemblage). Fusulinaceans and colonial rugose corals locally occur in Artinskian strata (Bryonoderm-extended assemblage). Small patch reefs and larger reef-mounds are locally developed in Artinskian deposits. No reefs have been encountered in Kungurian and younger strata. There is little evidence of meteoric-pedogenic diagenesis in subaerially exposed Artinskian carbonates and none in post-Artinskian sediments. Artinskian and younger shallow-water Bryonoderm carbonates are thoroughly cemented by clear sparry calcite of shallow and relatively early burial origin. Latest Permian (undetermined Kazanian-Tatarian) shallow-water sediments are dominated by spiculitic chert (Hyalosponge assemblage) with minor lenses and patches of variably silicified Bryonoderm carbonates.