Magnetostratigraphy of Quaternary and late Tertiary sediments on Banks Island, Canadian Arctic Archipelago

Abstract

Sediments approximately 50 m thick from Banks Island (Canadian Arctic Archipelago) contain one of the longest terrestrial records of Pleistocene climate changes in North America. Samples have been obtained from 126 horizons distributed among four localitites, of which 116 horizons yielded acceptable paleomagnetic data. In sediments of the Matuyama Reversed Zone, there are recorded at least two and possibly as many as five full continental glaciations, two interglacial intervals, and a nonglacial interval at the beginning which is considered preglacial. Subzones attributable to the Olduvai and Jaramillo are present within the Matuyama Reversed Zone. The Brunhes Normal Zone records three full continental glaciations and three interglaciations. The Brunhes-Matuyama boundary occurs within interglacial deposits. The preglacial Worth Point Formation records a climate milder than today, and cooler than that of the late Tertiary. Based on floral, faunal, stratigraphic, and paleomagnetic constraints, a normal polarity sequence in the Worth Point Formation is assigned to the Olduvai normal polarity subzone (1.95-1.77 Ma). The earliest direct evidence of glaciation on Banks Island occurs in sediments that postdate the Worth Point Formation ( <<1.77 Ma). Consequently, in the western Canadian Arctic, the first continental glaciation postdated the first glaciation in the Canadian Cordillera (2.6 Ma) by at least a million years. The overall mean direction of the Quaternary geomagnetic field in Banks Island does not differ significantly from the geocentric axial dipole field, and these sediments contain no inclination error.