Geochemical study of lower Eocene volcanic ash layers from the Alpine Anthering Formation, Austria.

Huber, Heinz; Koeberl, Christian; Egger, H.

doi:10.2343/geochemj.37.123

Cited by 11 publications

(7 citation statements)

References 38 publications

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“…Alternately, Ir peaks are found at major geologic boundary layers with no confirmed impacts, and at least some of those Ir concentrations may have resulted from volcanism. However, no major North American volcanic episode is known at 12.9 ka, and, according to Koeberl (39), such events produce Ir abundances of Ͻ0.5 ppb, much less than we find in the YDB. Therefore, the high concentrations of Ir do not appear to be of volcanic origin.…”

Section: Discussioncontrasting

confidence: 41%

Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling

Firestone

West²,

Kennett³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

476

639

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A carbon-rich black layer, dating to Ϸ12.9 ka, has been previously identified at Ϸ50 Clovis-age sites across North America and appears contemporaneous with the abrupt onset of Younger Dryas (YD) cooling. The in situ bones of extinct Pleistocene megafauna, along with Clovis tool assemblages, occur below this black layer but not within or above it. Causes for the extinctions, YD cooling, and termination of Clovis culture have long been controversial. In this paper, we provide evidence for an extraterrestrial (ET) impact event at Х12.9 ka, which we hypothesize caused abrupt environmental changes that contributed to YD cooling, major ecological reorganization, broad-scale extinctions, and rapid human behavioral shifts at the end of the Clovis Period. Clovis-age sites in North American are overlain by a thin, discrete layer with varying peak abundances of (i) magnetic grains with iridium, (ii) magnetic microspherules, (iii) charcoal, (iv) soot, (v) carbon spherules, (vi) glass-like carbon containing nanodiamonds, and (vii) fullerenes with ET helium, all of which are evidence for an ET impact and associated biomass burning at Ϸ12.9 ka. This layer also extends throughout at least 15 Carolina Bays, which are unique, elliptical depressions, oriented to the northwest across the Atlantic Coastal Plain. We propose that one or more large, low-density ET objects exploded over northern North America, partially destabilizing the Laurentide Ice Sheet and triggering YD cooling. The shock wave, thermal pulse, and event-related environmental effects (e.g., extensive biomass burning and food limitations) contributed to end-Pleistocene megafaunal extinctions and adaptive shifts among PaleoAmericans in North America.comet ͉ iridium ͉ micrometeorites ͉ nanodiamonds ͉ spherules

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Section: Discussioncontrasting

confidence: 41%

Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling

Firestone

West²,

Kennett³

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

476

639

View full text Add to dashboard Cite

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“…The generation of explosive eruptions of basaltic magmas requires either an explosive interaction of lavas and incoming water or magma with high primary volatile concentrations and unusually high temperatures (Pedersen and Jorgensen 1981). Specific intrinsic features of the NAIP magmas are suggested by the unusually high iridium concentrations (200-400 ppt) in the ashes; such values lie in the upper end of the concentration range reported for basaltic rocks (Schmitz and Asaro 1996;Huber et al 2003). This might indicate that the volcanism was related to magmas derived from Fig.…”

Section: Discussionmentioning

confidence: 91%

“…In the immobile element diagram of Winchester and Floyd (1977) this layer plots at the border between trachyte and trachyandesite, whereas more detailed geochemical investigations indicate a rhyolitic composition of the original magma (Huber et al 2003;Larsen et al 2003). Some of the ashes of the positive series have also been found at many other sites in Denmark, the North Sea, England, the Goban Spur Southwest of Ireland, and the Bay of Biscay (Knox 1984).…”

Section: Introductionmentioning

confidence: 90%

“…Based on detailed multistratigraphic and geochemical investigations, the most distal equivalents of layer +19 and 22 other layers have been identified in the Anthering and Untersberg outcrops ( Fig. 1) of the Austrian Alps near Salzburg (Egger et al 2000(Egger et al , 2005Huber et al 2003). These correlations were a prerequisite for the calculation of the eruption volumes.…”

Section: Introductionmentioning

confidence: 99%

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Gigantic volcanic eruptions and climatic change in the early Eocene

Egger

Brückl

2006

Int J Earth Sci (Geol Rundsch)

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23 layers of altered volcanic ash (bentonites) originating from the North Atlantic Igneous Province have been recorded in early Eocene deposits of the Austrian Alps, about 1,900 km away from the source area. The Austrian bentonites are distal equivalents of the ''main ash-phase'' in Denmark and the North Sea basin. We have calculated the total eruption volume of this series as 21,000 km 3 , which occurred in 600,000 years. The most powerful single eruption of this series took place 54.0 million years ago (Ma) and ejected ca. 1,200 km 3 of ash material, which makes it one of the largest basaltic pyroclastic eruptions in geological history. The clustering of eruptions must have significantly affected the incoming solar radiation in the early Eocene by the continuous production of stratospheric dust and aerosol clouds. This hypothesis is corroborated by oxygen isotope values, which indicate a global decrease of sea surface temperatures between 1 and 2°C during this major phase of explosive volcanism.

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“…Still more distant from the eruption centre are records in the area of the former Tethys Ocean. Bentonite layers have been reported from the Austrian Alps (Egger 1995;Huber et al 2003;Egger and Brückl 2006), the Polish Outer Carpathians (Cieszkowski et al 2006) and the Swiss Gurnigel nappe (Winkler et al 1985), suggesting a deposition of distal equivalents more than 2000 km away from the source area (Fig. 1).…”

Section: Introductionmentioning

confidence: 92%

Early Eocene volcanic ashes on Greifswalder Oie and their depositional environment, with an overview of coeval ash-bearing deposits in northern Germany and Denmark

Obst

Ansorge

Matting

et al. 2015

Int J Earth Sci (Geol Rundsch)

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Unconsolidated bentonites and carbonate-cemented volcanic ashes occur in northern Germany within the clay sequence of the Lamstedt and Schlieven Formations documented by several wells. Ash-bearing carbonate concretions (so-called cementstones) are also known from glacially transported rafts and erratic boulders on the Baltic Sea island Greifswalder Oie, representing the easternmost exposures of early Eocene sediments in the North Sea Basin. The ashes can be correlated with water-lain ashes of the Danish Fur and Ølst Formations (mo-clay) generated during the opening of the North Atlantic Ocean about 55 Ma ago. Two types of cementstones can be distinguished on the basis of the mineralogical composition, sedimentary features and fossil content. Greifswalder Oie type I contains a black, up to 12-cm-thick ash deposit that follows above two distinct thin grey ash layers. The major ash unit has a rather homogeneous lower part; only a very weak normal grading and faint lamination are discernible. In the upper part, however, intercalations with light mudstone, in part intensively bioturbated, together with parallel and cross-lamination suggest reworking of the ash in a shallow marine environment. Major and trace element compositions are used to correlate type I ashes with those of the Danish-positive series which represent rather uniform ferrobasalts of the Danish stage 4, probably related to the emergence of proto-Iceland. In contrast, type II ash comprises a single, normally graded, about 5-cm-thick layer of water-lain air-fall tuff, which is embedded in finegrained sandstone to muddy siltstone. Type II ash is characterised by very high TiO 2 but low MgO contents. Exceptional REE patterns with a pronounced positive Eu anomaly suggest intense leaching of the glass that hampers exact correlation with pyroclastic deposits within the North Atlantic Igneous Province.

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Geochemical study of lower Eocene volcanic ash layers from the Alpine Anthering Formation, Austria.

Cited by 11 publications

References 38 publications

Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling

Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling

Gigantic volcanic eruptions and climatic change in the early Eocene

Early Eocene volcanic ashes on Greifswalder Oie and their depositional environment, with an overview of coeval ash-bearing deposits in northern Germany and Denmark

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