A new whitefish from the early Quaternary of Bluefish Basin, Yukon Territory, Canada, and its paleoenvironmental implications

Abstract

A nearly complete fossil of a whitefish, Coregonus beringiaensis sp. nov. (Salmoniformes: Salmonidae: Coregoninae), the oldest known record of the genus, is described from Ch’ijee’s Bluff along the Porcupine River, Bluefish Basin, Yukon Territory. The new species is closest to but distinct from species within the Coregonus clupeaformis complex, especially in its low lateral line scale count, quadrate with an extensive canal and pore complex, Y-shaped lachrymal, and a unique combination of counts and measurements of fins, scales, and body proportions. The stratigraphic position of the source concretionary layer, at the base of unit 3, a lacustrine unit, is well below a magnetically reversed interval thought to represent at least the upper part of the Matuyama Chron. The specimen was found above ice-wedge pseudomorphs thought to be the first sign of the onset of cold temperatures in the early Quaternary. The fossil is older than 0.79 Ma and probably younger than 2.58 Ma. Palynomorphs in the concretion suggest an open shrub-tundra environment and a climate colder than that of the present, similar to conditions prevailing at or above the tree line, and a good fit for preglacial conditions in the early Quaternary. Sedimentary and geochemical analyses suggest that fossilization occurred in an environment characterized by fine sedimentation in a cold, reducing milieu with a pH of ∼7.5. Alternatively, these conditions may reflect the postdepositional or early diagenetic environment. The lake in which the whitefish lived was possibly part of a hydrographic basin draining toward the Arctic Ocean.