Lower Permian brachiopods and molluscs from the upper Jungle Creek Formation, northern Yukon Territory, Canada

Abstract

The study aims to provide a comprehensive systematic account of Lower Permian brachiopods and molluscs (excluding gastropods) from the upper Jungle Creek Formation in northern Yukon Territory, western Canada, and to assess their biostratigraphic and paleoecological significance. Sixty-nine brachiopod species belonging to 53 genera, six bivalve species belonging to five genera, and one ammonoid species are described and illustrated. New taxa include Arctitreta peelensis n. sp., Orthotetes canadensis n. sp., Liosotella compacta n. sp., Anemonaria auriculata n. sp., Costispinifera paucispinosa n. sp., Rugivestis arctica n. sp., Thamnosia spinosa n. sp., Globiella costellata n. sp., Protoanidanthus umbonatus n. sp., Rhynoleichus dorsoconvexa n. sp., Septacamera triangulata n. sp., Composita bamberi n. sp., Ogilviecoelia inflata n. gen. et sp., Tumarinia yukonica n. sp., Yukonella plana n. gen. et sp., Timaniella convexa n. sp., Yukonospirifer yukonensis n. gen. n. sp., Larispirifer ettrainensis n. sp., Domokhotia junglensis n. sp., Tiramnia canadica n. sp., and Retimarginiferinae n. subfam. The three brachiopod biozones previously recognized within the upper Jungle Creek Formation are revised and substantiated. These are the (in ascending stratigraphic order) Yakovlevia transversa Assemblage Zone, Ogilviecoelia inflata Assemblage Zone, and Jakutoproductus verchoyanicus Assemblage Zone. The distribution of these zones in the study area and their correlation with other major Lower Permian marine sequences in North America and the Arctic are discussed. Close correlation of the Yukon brachiopod faunas with those from the Urals, northeast Russia, and the Canadian Arctic, reinforced by some data from fusulinids and ammonoids, suggests that the Yakovlevia transversa Zone is probably Early Sakmarian (Tastubian) in age, the Ogilviecoelia inflata Zone is Late Sakmarian (Sterlitamakian), and Jakutoproductus verchoyanicus Zone is Early Artinskian (Aktastinian). A computerized ordination technique (principal components analysis) is used to delineate recurrent paleocommunities. Four fossil communities are recognized: Rhynchopora magna, Fimbrinia-Tubersulculus-Kutorginella, Ogilviecoelia inflata, and Tityrophoria nelsoni- Septacamera triangulata. These paleocommunities are analyzed in terms of faunal composition and possible depositional environments. They seem to record positions in an onshore to offshore sequence across a shallow marine shelf, with the Rhynchopora magna paleocommunity possibly representing a shallow subtidal restricted zone; the Fimbrinia-Tubersulculus-Kutorginella paleocommunity representing probably an open shelf, above wave base zone; the Ogilviecoelia inflata paleocommunity possibly an open shelf, near or at wave base zone; and the Tityrophoria nelsoni-Septacamera triangulata paleocommunity a low energy position, farther offshore, below wave base.