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 40 Ar/ 39 Ar 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.

ABSTRACT Volcanoes that interact with the cryosphere preserve indicators of their eruption environments. These glaciovolcanoes and their deposits have powerful potential as proxies of local and global paleoclimates. The Garibaldi volcanic belt is the northern (Canadian) segment of the Cascade volcanic arc. In this study, we compiled a comprehensive database of Quaternary volcanic landforms and deposits in the Garibaldi volcanic belt. We found that the region exhibits a high degree of volcanic diversity, and a significant component of this diversity is due to the abundance of glaciovolcanoes. These include: tuyas, tindars, subglacial tephra cones, ice-impounded lavas, subglacial domes and breccias, subglacial lava flows, and lava-dominated tuyas. As a group, they inform the presence, thickness, and transient properties of ancient, continental-scale ice sheets (i.e., the Cordilleran ice sheet) that have waxed and waned in thickness and extent across the region. We ascribe much of the character of glaciovolcanism in the Garibaldi volcanic belt to a wide range of magma compositions (alkaline basalt to rhyolite) and to the extreme relief of the landscape. We used forensic volcanologic evidence, in conjunction with our database, to define a terrestrial-based reconstruction of ice-sheet thickness and extent that spans the latter half of the Quaternary (i.e., past ~1 m.y.). We then compared our reconstruction to the marine isotope stage (MIS) record and found a number of positive correlations and discordances. We show glaciovolcanoes to be an excellent, and underutilized, proxy for Earth’s paleoclimate, and a powerful tool for reconstructing ice sheets predating the last glaciation.

The origin and evolution of Mars’s inventory of volatile elements is pivotal to a wide range of physical, chemical, geological, and biological issues and concerns. The identification of subglacially erupted volcanoes on Mars suggests that ice sheets existed at high and low latitudes repeatedly over geological time, but the importance of those volcanoes is not just as a simple Boolean climate signal. Like terrestrial subglacially erupted volcanoes, they can potentially yield a more holistic range of paleoenvironmental parameters, including ice thickness, thermal regime, and surface elevation. On Earth, at least nine different types of terrestrial subglacial volcanic successions can be identified using landform characteristics, lithofacies, and sequence architecture. The principal characteristics of each are reviewed in this paper, together with the first empirical comparative analysis of the morphometry of the landforms. All were probably erupted in association with wet-based ice and there are different implications for volcanic landforms erupted under different glacial thermal regimes (polar, subpolar). However, they represent our best sources of information with which to assess Mars analogs, some of which (as on Earth) may have been the source of megascale meltwater outburst floods. Applying the results of this paper to three different morphological types of candidate subglacial volcanoes on Mars indicates that it is difficult to suggest a plausible glaciovolcanic analogy for Mars’s tall cones ; they more closely resemble pyroclastic mounds erupted subaerially or subaqueously, under ice-free conditions. Conversely, Mars’s low-domes may be very extensive, inflated, subglacial “interface sills” formed under comparatively thick ice of any thermal regime. Finally, the very large, flat-topped constructs on Mars resemble mafic tuyas emplaced in thick (up to 2 km) temperate ice. However, because of their very large size compared to terrestrial analogs, the possibility also exists that the latter are polygenetic stratovolcanoes, formed subglacially either within very thick ice, or as multiple superimposed lava-fed deltas emplaced in much thinner ice that repeatedly re-formed on the volcanoes after each eruptive episode. A plausible terrestrial analogy for the latter is the long-lived James Ross Island stratovolcano in Antarctica.

Abstract 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 km 3 ) 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.

Abstract Dissolved H 2 O, CO 2 , S and Cl concentrations were measured in glasses from Tanzilla Mountain, a 500 m-high, exposed subglacial volcano from the Tuya–Teslin region, north central British Columbia, Canada. The absence of a flat-topped subaerial lava cap and the dominance of pillows and pillow breccias imply that the Tanzilla Mountain volcanic edifice did not reach a subaerial eruptive phase. Lavas are dominantly tholeiitic basalt with minor amounts of alkalic basalt erupted at the summit and near the base. Tholeiites have roughly constant H 2 O ( c. 0.56 ± 0.07 wt%), CO 2 (<30 ppm), S (980 ± 30 ppm) and Cl (200 ± 20 ppm) concentrations. Alkalic basalts have higher and more variable volatile concentrations that decrease with increasing elevation (0.62–0.92 wt% H 2 O, <30 ppm CO 2 , 870–1110 ppm S and 280–410 ppm Cl) consistent with eruptive degassing. Calculated vapour saturation pressures for the alkalic basalts are 36 to 81 bars corresponding to ice thicknesses of 400 to 900 m. Maximum calculated ice thickness ( c. 1 km) is at the lower end of the range of predicted maximum Fraser glaciation ( c. 1–2 km), and may indicate initiation of volcanism during the waning stages of glaciation. Temporal evolution from tholeiitic to alkalic compositions may reflect compositional gradients within a melting column, instead of convective processes within a stratified magma chamber. The mantle source region for the subglacial volcanoes is enriched in incompatible elements similar to that for enriched mid-oceanic ridge basalt (e.g. Endeavour Ridge) and does not contain residual amphibole. Thus, metasomatic enrichment most likely reflects small degree partial melts rather than hydrous fluids.