PERMIAN WARM- TO VERY COLD-WATER CARBONATES AND CHERTS IN NORTHWEST PANGEA

Abstract

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 theAsselian and Sakmarian interval cool to cold temperate like conditions occurred during the Artinskian to Kazanian interval and very cold polar like conditions were es tablished during latest Permian time undetermined Kazanian Tatarian This climatic deterioration led to asignificant shift in the composition of biogenic sediments Asselian and Sakmarian shallow watercarbonates comprise abundant aragonite secreted skeletal and non skeletal elements ooid cement dominated by abundant green algae and foraminifers as sociated 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 fortens ofkilometers Submarine ce ments 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 bryo zoans echinoderms and brachiopods Bryonoderm assemblage Fusulinaceans and colonial rugose corals locally occur in Artinskian strata Bryonoderm exIended assemblage Small patch reefs and larger reef mounds are locally developed in Artinskiandeposits No reefs have been en countered in Kungurian and younger strata There is little evidence of meteoric pedogenic diagenesis in subaerially exposed Artinskian carbonates and none in post Artinskiansediments Artinskianand younger shallow waterBryonoderm carbonates are thoroughly cemented by clearsparry cal citeof shallow and relatively early burial origin Latest Permian undetermined Kazanian Tatarian shallow watersediments are dominated by spic ulitic chert Hyalosponge assemblage with minor lenses and patches ofvariably silicified Bryonoderm carbonates