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

摘要

Two distinct dust layers in the EPICA-Dome C ice core (75 degrees 06'S, 123 degrees 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.