A volcanic marker (92 ka) for dating deep east Antarctic ice cores

International audienceTephra layers recorded in East Antarctic ice enable reliable linking over long distances and, when correlated with well-dated eruptions in the source area, provide absolute ages for improving the accuracy of model-based ice chronology. We used chronostratigraphic information and grain-specific geochemical data (major elements by electron microprobe and trace elements by LA-ICP-MS) to suggest that a tephra layer from the EPICA-Dome C and Dome Fuji ice cores is the distal counterpart of the Mt. Berlin (Marie Byrd Land province, West Antarctica) pyroclastic unit 40Ar/39Ar dated to 92.5±2.0 and 92.2±0.9 ka. Such one-to-one correlation, which is proposed here for the first time for the East Antarctic deep climatic archives, provides independent age constraints for glaciological modelling of core timescales

Corrigendum to ;Last glacial tephra layers in the Talos Dome ice core (peripheral East Antarctic Plateau), with implications for chronostratigraphic correlations and regional volcanic history; [Quaternary Sci. Rev. 165 (2017) 111-126]

International audienceWhen this paper was originally published there was an error in Table 1. The age of the TD sample 914 should be 26.16 ± 0.71 (not 21.16 ± 0.71). The correct Table 1 is printed below

Extended East Antarctic ice-core tephrostratigraphy

International audienceThree new tephra layers have been identified and analysed in the deeper sections of the EPICA Dome C (EDC) and Vostok ice record (East Antarctic plateau): one from EDC (358 ka old), originated from an Antarctic volcano, and two from Vostok (406 and 414 ka old, respectively), which are related to Antarctic volcanoes and to southern Andes and/or Antarctic Peninsula centres, respectively. These layers represent the oldest tephra-bearing events so far detected in deep polar ice cores and extend the regional tephrostratigraphic framework back to the fourth climatic cycle. Although differences between the drill sites are observed, new and previously published tephra data from deep ice cores broadly confirm that the clockwise circum-Antarctic atmospheric circulation played a major role in the dispersal of volcanic dust onto the plateau. While the last 220-ka core sections contain about a dozen visible tephra fall layers, the ice representing the time interval from 220 ka back to 800 ka (i.e. the EDC core bottom) is almost devoid of observed tephras. Although it is possible that the reduced frequency is an observational artefact, the observed pattern could alternatively reflect late Quaternary activity fluctuations of sources for tephra in the East Antarctic plateau, particularly South Sandwich Islands, with enhanced explosive activity in the last two glacial cycles with respect to previous periods

First discovery of meteoritic events in deep Antarctic (EPICA-Dome C) ice cores

International audienceTwo distinct dust layers in the EPICA-Dome C ice core (75°06′S, 123°21′E, East Antarctic Plateau) have been shown to relate to individual meteoritic events. Particles forming these layers, investigated by electron microprobe, show peculiar textural, mineralogical and geochemical features and closely resemble extraterrestrial debris in deep-sea sediments and polar caps. Preliminary estimates of cosmic debris input at the studied layers, obtained from Coulter Counter measurements, are 4–5 orders of magnitude greater than the yearly micrometeorite flux in East Antarctic snow and ice. The cosmic events are accurately dated through glaciological models at 434 ± 6 and 481 ± 6 ka, respectively and are located in the core climatic stratigraphy near the “Mid-Brunhes Event”. This is the first report of well-dated cosmic horizons in deep Antarctic ice cores. It significantly improves the extraterrestrial record of Antarctica and opens new correlation perspectives between long climatic records of the South polar region

A 70 ka record of explosive eruptions from the TALDICE ice core (Talos Dome, East Antarctic plateau)

The new Antarctic TALDICE ice core (72° 49' S, 159° 11' E, 1620 m depth), containing abundant primary tephras, provides the opportunity to elucidate the late Quaternary volcanic history of the south polar region, as well as to broaden the East Antarctic tephrostratigraphic framework. Here grain size and glass compositional data for representative tephra layers from the last 70 ka core section are used for source identification. Results point to origin of layers from centres of the Melbourne Volcanic Province (McMurdo Volcanic Group), located ~250 km from the coring site. Occurrence of tephra layers within the ice core record suggests that explosive activity in the identified source was not constant over the considered period, with a minimum of activity between 20 and 35 ka, and increased activity back to 65 ka. In addition to palaeovolcanic implications, the TALDICE tephra layers offer prospects for firm correlations between diverse widely separated palaeoarchives and for accurate dating of the Antarctic climatic record. Copyright © 2010 John Wiley & Sons, Ltd

Last glacial tephra layers in the Talos Dome ice core (peripheral East Antarctic Plateau), with implications for chronostratigraphic correlations and regional volcanic history

International audienceTephra isochrons offer considerable potential for correlating diverse palaeoarchives and highlighting regional climatic differences. They are especially useful when applied to polar ice records encompassing the last glacial, as these clearly portray the pronounced millennial-scale climate variability that characterised this period. Here we present the continuous record of primary fallout tephra layers in the East Antarctic Talos Dome ice core (72°49‧S, 159°11‧E), developed upon examination of the core sections spanning the glacial period 16.5 to 71 ka. A total of ca. 45 discrete tephra deposits precisely positioned stratigraphically relative to the temperature record for the core and dated using the AICC2012 timescale, were identified. Quantitative grain size, particle morphology, major and trace element composition using Coulter Counter, SEM, EPMA-WDS, and LA-ICP-MS analytical methods were studied as diagnostic features for tephra characterisation. The tephrostratigraphic framework provides a reference for future precise comparison between ice and sediment sequences across the Antarctic continent. Indeed, several potential markers characterised by distinct volcanic glass geochemistry and/or particular stratigraphic location (e.g., a 17.6-ka ash layer deposited during the well-known major acidity event) are now available for the direct linkage of palaeoclimatic archives. The Talos Dome tephra sequence, dominated by mid-distal pyroclastic products from the nearby Northern Victoria Land volcanoes, also represents the most comprehensive and best time-constrained record of regional Antarctic volcanism yet developed. It documents nearly continuous sustained explosive activity during the considered time interval and, combined with previous ice-core tephra results for the last and the current interglacial periods, suggests progressive compositional shift through time

Multiple sources for tephra from AD 1259 volcanic signal in Antarctic ice cores

International audienceStrong volcanic signals simultaneously recorded in polar ice sheets are commonly assigned to major low-latitude eruptions that dispersed large quantities of aerosols in the global atmosphere with the potential of inducing climate perturbations. Parent eruptions responsible for specific events are typically deduced from matching to a known volcanic eruption having coincidental date. However, more robust source linkage can be achieved only through geochemical characterisation of the airborne volcanic glass products (tephra) sometimes preserved in the polar strata. We analysed fine-grained tephra particles extracted from layers of the AD 1259 major bipolar volcanic signal in four East Antarctic ice cores drilled in different widely-spaced locations of the Plateau. The very large database of glassshard geochemistry combined with grain size analyses consistently indicate that the material was sourced from multiple distinct eruptions. These are the AD 1257 mega-eruption of Samalas volcano in Indonesia, recently proposed to be the single event responsible for the polar signal, as well as a newly-identified Antarctic eruption occurred in AD 1259. Finally, a further eruption that took place somewhere outside Antarctica has contributed to tephra deposition. Our high-resolution, multiple-site approach was critical to reveal spatial heterogeneity of tephra at the continental scale. Evidence from ice-core tephra indicates recurrent explosive activity at the Antarctic volcanoes and could have implications for improved reconstruction of post-volcanic effects on climate from proxy polar records