A masterful and comprehensive effort here from Comet Research Group co-author, Bill Mahaney. Much of the discipline-specific text is hard for the Tusk to fully grasp, and I have had no time to properly review, but I have asked Bill to provide a layman’s summary of the approach and conclusions. I hope to post this soon.
Mount Viso (3841 m asl), one of the highest mountains in the Western European Alps carries not only a glacial record following the end of the last glacial (Late Glacial-LG), but also a cosmic airburst record at approximately ~ 12.8 ka, presumably the black mat, that adds to a worldwide record of biomass burning which is considered to have triggered the Younger Dryas (YD) cooling episode. We combine the stratigraphic evidence of staggered Late Glacial retreat on both sides of the continental divide—faster in the upper Guil, possibly slower in the upper Po valleys—followed by superposed YD moraine overlapping LG in France, and stillstand of LG with overlapping YD in Italia with recovered cosmic evidence. Previously, we studied selected areas on the Viso massif, but here we expand on newly combined stratigraphic-cosmic airburst evidence, the latter lying in an uneven distribution of welded, melted and air-quenched clasts of pebble to sand-silt size in paleosols, all of which carry variable high to low REEs, high base metals, partial Pt and Ir coated surfaces indicative of nuclear-cosmic events. One of the outstanding conclusions of this research is the indisputable close correspondence of widespread cosmic airburst evidence with the YDB (Younger Dryas boundary) and onset of the YD. Thus, a test of catastrophism, firmly embedded in surficial sediment, yields some important underpinnings of Earth’s climatic history.
Whereas we hypothesize that the theorized cosmic event was caused by an airburst fragment or fragments sourced from Earth’s encounter with the Encke Comet (12.8 ka)(Napier 2010), thereafter exploding over the Mt. Viso area, while others argue that such an encounter could not sustain the cooling event that followed. The Earth/comet impact is thought to have occurred over southern Manitoba, melting part of the Laurentide Ice Sheet in the process, spewing fragments southward in an arc southwest to east–northeast.Other fragmental bodies of the impact continued to encounter Earth as the Taurid meteors. As hypothesized further by Mahaney et al. (2013b), during the YD, − 12.8 ka to ~ 11.6 ka, the meteor swarm was possibly of sufficient mass to maintain positive glacial mass balances in various alpine localities in North and South America and in the Alps, thus sufficient to sustain the YD glacial resurgence linked to the main cosmic event. Whether the YD cooling event was caused conclusively by one or the other—the thermohaline circulation or the widespread fragmental explosions— the upshot is that the YD is firmly documented by palynological and geological evidence on a worldwide basis. The marine argument by itself does not explain the worldwide YD effect, but it does reinforce regional cooling and augment intercontinental cooling imposed by instantaneous
Many geologists, infused with the notion of uniformitarianism, as proposed by Lyell (1830), are reluctant to entertain a possible catastrophic mechanism for the YD (Kennett et al. 2007), that is, a cosmic event to explain changes in the earth-atmosphere system such that solar-induced warming might be offset for nearly 1300–1400 years by the YD glacial advance. As discovered by palynologists decades ago, a drastic change in the distribution of a widespread cold-loving alpine wildflower, a member of the rose family—Dryas octapetala—causing it to expand its area of coverage, thus increasing for a time its pollen count in retrieved cores, lent its name to the Late Pleistocene YD climatic episode. Because the Mt. Viso Massif, one of the highest areas in the Western Alps, is surrounded by valley glaciers that responded to off-again, on-again rapid changes in snow balance at the end of the ice age (Würm in the Alps, Pinedale in the Rocky Mountains; Liki on Mt. Kenya), it is an obvious laboratory in which to study the YD in relation to earlier warming (LG) and late Holocene cooling (LIA).
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