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The Mount Meager volcanic complex (MMVC) is one of the eight major calc-alkaline volcanic centres within the Garibaldi Volcanic Belt, Canada. MMVC volcanism spans ∼2 Ma and has been mainly intermediate to felsic in composition. However, small-volume mafic centres are located around the periphery of the Mount Meager massif and have been collectively referred to as the Mosaic Assemblage or Mount Meager basalts. Here, we present new 40Ar/39Ar ages and expanded chemical datasets for the MMVC mafic rocks. We show that mafic eruptive ages are both older and longer-lived than previously interpreted, spanning the last ∼450 ka, and occurring in four episodes at ∼440, 200, 106, and 17 ka. We also found that chemical signatures for the MMVC mafic rocks have evolved across the four periods, fluctuating from “OIB”-like melt characteristics to more typical slab-influenced, calc-alkaline, before returning to “OIB”-like in the youngest phase. These findings provide the first evidence of a temporal-chemical evolution of melt sourcing for the Garibaldi belt volcanism. Lastly, field mapping has identified edifices and deposits that are glaciovolcanic in origin (vs. nonglaciovolcanic), which were used in conjunction with our new 40Ar/39Ar age estimates to document the presence or absence of Coast Mountain sectors of earlier Cordilleran ice sheets in southwest British Columbia over the last 500 ka.

Swan Valley is a graben in eastern Idaho that formed by extension along the Grand Valley and Snake River faults and preserves a record of explosive rhyolitic volcanism sourced from the Yellowstone Plateau and Heise volcanic fields, as well as locally sourced basaltic lavas. The Pleistocene Basalt of Antelope Flat intersected the South Fork of the Snake River and generated a temporary hyaloclastite dam. Previous workers proposed that the lava dam allowed for the accumulation of water that led to the generation of paleo-Swan Lake. Although lacustrine deposits from paleo-Swan Lake have not been described or mapped, several-meters thick intercalated hyaloclastites and pillow lavas require the interaction between continued volcanism and standing water. In this work, we present new geochemical, geochronologic, and paleomagnetic data to reinterpret the eruptive history of the basalts within the valley, estimate the volume and duration to fill paleo-Swan Lake, and calculate incision rates of the Snake River through Quaternary basalts. Using geochemical and paleomagnetic data, we reinterpret deposits previously mapped as the Basalt of Antelope Flat as three temporally distinct units. The duration to fill paleo-Swan Lake is calculated as 12 to 20 years. An absence of lacustrine deposits, shorelines, or other indicators of a lake environment led us to propose that shallow, marshy, wetland conditions existed locally to produce hydrovolcanic deposits characteristic of the Basalt of Antelope Flat. We report a new 40Ar/39Ar age of 904 ± 11 ka (2σ) for the Basalt of Antelope Flat, which we use to determine an average incision rate of 0.014 cm/yr for the Snake River through Quaternary basalts. Our multi-method approach provides updated constraints to the eruptive and geomorphological history of southeastern Idaho.

This paper presents a preliminary study of the Middle Palaeolithic lithic industries recovered at six selected open-air sites in the Latium region (central Italy), part of a regional cultural complex known as the “Pontinian”. The pedo-stratigraphic analysis combined with 40Ar/ 39Ar age constraints on the sites permits us to provide for the first time a geomorphological and chronological (300–40 ka) framework for several open-air sites in central Italy. The temporal range is remarkably coincident with the Neanderthal presence in this region. Moreover, the lithic collections analysed include the oldest occurrence of a Mousterian industry in this region. The present work, therefore, provides the background context for future re-evaluation of the peculiar Pontinian techno-complex through a more in-depth technological approach and its comparison with the other Neanderthal occurrences in central Italy.

Santorini Volcano, located in the central sector of the South Aegean volcanic arc, is one of the most active and potentially dangerous volcanoes in Europe. It has hosted Plinian eruptions over the last 350 ka of which at least four eruptions were accompanied by caldera collapses. Even though Santorini Volcano is considered a major threat, the main focus of research, thus far, has been on the comparatively young and subaerial deposits, whereas older stages of volcanism have been poorly studied. Our study focusses on samples from the submarine inner caldera walls and gives new insights into the early evolutionary stages of Santorini Volcano, contributing to a better understanding of its eruptive history and thus potential risks. The submarine lava successions were sampled along the inner caldera wall by a remotely operated vehicle (ROV) during R/V POSEIDON cruise 511 in 2017. The recovered lavas comprise two magmatic series, a low-K basaltic series overlain by a medium- to high-K series, which includes basaltic andesites, andesites and occasional dacites to trachytes. Major and trace element compositions and mineral zonation patterns suggest that fractional crystallisation and periodic magma replenishment were the dominant processes controlling magma evolution of both magmatic series. In addition, repeated magma mixing events played an important role, as indicated by zonation patterns in plagioclase and clinopyroxene ante- and phenocrysts. The thickness of the submarine lava successions (≥100 m) and the occurrence of similarly zoned plagioclase throughout, indicate long-lived magma plumbing systems characterised by repeated processes. Furthermore, the incompatible element and radiogenic isotope ratios indicate a heterogeneous mantle source for Santorini magmas, which reflects the relative contribution of subduction (sedimentary) input and mantle wedge influx. A lava sample from the northern submarine caldera wall probably represents a deep level of the original Peristeria volcano. 40Ar/39Ar dating of andesite lavas from the southern submarine caldera produced ages of ~255 ka, whereas one basalt lava produced an age of 309 ± 30 ka. Interestingly, the new ages of both groups fall within an age gap in the volcanic history of Santorini Volcano. Even though it was not possible to unequivocally correlate the sampled submarine lava series to known subaerial units, the major and trace element compositions, and Sr-Nd-Pb isotopic compositions of our intermediate lavas show a strong similarity to subaerial lavas of Peristeria volcano, the second oldest major stage of Santorini volcanism. Nevertheless, it seems more likely that we have sampled so far unknown stages of volcanism at Santorini Volcano.

International audience; In the Central Andes, large (> 500 km2) and long-lived (1–5 Ma) volcanic clusters (LVCs) are less explored and their eruptive history and magmatic regimes less understood than smaller, short-lived (