Biostratigraphy of the Ladinian–Carnian (Middle–Late Triassic) boundary section at Glacier Spur, northeastern British Columbia, Canada

Strata exposed at the Glacier Spur section, located in northeastern British Columbia, Canada, were deposited during the Ladinian–Carnian (Middle–Late Triassic) boundary interval. The definition of the base of the Carnian stage at the Global Boundary Stratotype Section and Point (GSSP) at Prati di Stuores/Stuores Wiesen in Italy permits re-assessment of this boundary in North America. New conodont and ammonoid collections have been made from Glacier Spur and studied together with existing collections; both faunas are described taxonomically in this paper. The collections include the occurrence of the ammonoid Daxatina canadensis, the index fossil for the base of the Carnian stage, in the Liard Formation, which is the first discovery of this species in the formation. This indicates that the Liard Formation is at least partially Carnian in age. The Ladinian–Carnian boundary at Glacier Spur is placed at the first occurrence of D. canadensis, at a level 259.3 m above the base of the section. D. canadensis occurs with the conodont Quadralella intermedius, which is interpreted to be a proxy for the boundary in North America. The occurrence of these fossils allows correlation of the Glacier Spur section with sections in British Columbia and Nevada, as well as with the GSSP in Italy. It is proposed that the latest Ladinian/earliest Carnian Subzone 2 of the Sutherlandi ammonoid zone be re-defined or subdivided to emphasise the appearance of D. canadensis within the subzone.