Volcanism and glacial interaction in the Wells Gray–Clearwater volcanic field, east-central British Columbia

Chapter: This field guide describes a three-day trip from Vancouver, British Columbia, to the Wells Gray–Clearwater volcanic field (WGCVF) in east-central British Columbia. The WGCVF is the site of transitional to alkali olivine basaltic volcanism erupted over the last three million years. The small volume magmas (<1 km3) erupted along preexisting normal faults related to the late stages of Cordilleran terrane amalgamation, along the boundary between the miogeoclinal and pericratonic rocks of the Kootenay terrane and the allochthonous Slide Mountain and Quesnellia terranes west of ancestral North America. The magmas are highly enriched in incompatible elements, especially large-ion lithophile elements, and are interpreted as the result of low degrees of partial melting of a heterogeneous, metasomatized mantle. Upon ascent through the crust, they carried up both crustal and mantle xenoliths. During the eruptive period of the WGCVF, at least four glacial periods have occurred. The interplay between volcanism and glaciation is captured in the wide range of volcanic features found in the region. Field trip participants will view numerous diverse volcanic landforms and deposits: from tuyas to ice-marginal valley-edge deposits, volcanoclastic-lacustrine deposits, and associated pillow lavas and hyaloclastites.

Book: This volume, prepared for the 126th GSA Annual Meeting in Vancouver, Canada, offers guides to trips in the Cascadia subduction zone. The active tectonism of the region has had a profound effect on the bedrock and surficial geology of the area, and on human interactions with the geologic environment. These themes are reflected in the trips associated with the meeting. Trip topics relate to bedrock geology, volcanism and Cordilleran glaciation and deglaciation, as well as human interaction with the natural environment. The trips that discuss human interaction cover archaeology, natural hazards and the urban environment, as well as the role that local geology and tectonism have played in shaping colonization of the region since the last glaciation. The field guide volume has something for everyone! --From publisher description.