A 3 m.y. record of volcanism and glaciation in northern British Columbia, Canada

Abstract

The Tuya-Kawdy region of northern British Columbia is well established as a place where glaciation and volcanism overlapped in space. However, no modern work has integrated observations from the region’s volcanic and glacial deposits with geochronologic constraints to summarize how they might overlap in time. Here, we provide a general overview of such characteristics and 23 new 40Ar/39Ar eruption ages of glaciovolcanic deposits ranging from 4.3 Ma to 63 ka to constrain the timing, location, and minimum thicknesses and distributions of coincident ice. Subaerial lava fields interspersed with glaciovolcanism record periods of ice-sheet absence in presumably warmer climate conditions. These generally coincide with interglacial marine isotope stages. Many of the volcanoes have a secondary record of posteruption glacial modification, cirques, erratics, and mega-lineations, which document later climate changes up to the present. We used edifice-based terrain analysis to reconstruct changes to local minimum Cordilleran ice-sheet thicknesses, extents, and flow directions at specific locations and times during the late Pliocene and the Pleistocene.