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