A 500 ka record of glaciovolcanism in the Mount Meager volcanic complex, northern Garibaldi Volcanic Belt, Canada

The Mount Meager Volcanic complex (MMVC) is one of eight major volcanic centres within the Garibaldi volcanic belt, British Columbia, Canada. MMVC eruptive activity has spanned ~2 Ma and has mainly been intermediate to felsic in composition. However, small volume mafic (basaltic) centres are also located around the periphery of Mount Meager massif. Here we present new 40Ar/39Ar ages for the MMVC rocks spanning the last 500 ka during which time volcanism has coincided with many Pleistocene cycles (advance and retreat) of the Cordilleran Ice Sheet (CIS) within southwest British Columbia (SWBC). The presence or absence of ice at the time of an eruption is commonly expressed by edifice morphology and lithostratigraphic facies and organization. Thus, when volcanic rocks are precisely dated, they not only constrain the age of the eruption but can also inform on their eruptive environment (i.e., glacial or non-glacial). Each of our new age determinations is from a well-investigated volcanic occurrence that has been clearly identified as either glaciovolcanic or non-glaciovolcanic. We implement the age estimates and field parameters for each volcanic deposit into the geometric glacial models of Wilson et al., (2019) to reconstruct the evolving climates around the MMVC over the last 0.5 ma. We show that at ~500 ka, SWBC was nearly ice-free. At ~440 ka and ~200 ka respectively, thick ice sheets are modeled throughout SWBC. At ~106 ka we model a transition into a nearly ice-free environment, and lastly, we model the onset to the coalescence of the Last Glacial Maximum (e.g., Fraser Glaciation) at ~24 ka. These findings provide strong support for using volcano-ice interactions to reconstruct local, land-based glacial records.