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Short answer, I dunno. The same thought has crossed my mind. I would like to know about all the traces found in these ice cores, with a view of perhaps finding junk suggestive of bolide impacts and whatnot. Iridium was found in a layer laid down in Antarctica (if memory serves, and it sometimes doesn't, so I'll go look later) by the Eltanin impact 2 million years ago. And traces of an Alaskan volcano's eruption was found in one of the Greenland cores, although it was (of course) first attributed to the (IMHO fictional) mid-2nd millennium BC eruption of Thera.

Identification of Aniakchak (Alaska) tephra
in Greenland ice core
challenges the 1645 BC date
for Minoan eruption of Santorini
Nicholas J. G. Pearce
John A. Westgate and Shari J. Preece
Warren J. Eastwood
William T. Perkins
Minute shards of volcanic glass recovered from the 1645 ± 4 BC layer in the Greenland GRIP ice core have recently been claimed to originate from the Minoan eruption of Santorini [Hammer et al., 2003]. This is a significant claim because a precise age for the Minoan eruption provides an important time constraint on the evolution of civilizations in the Eastern Mediterranean. There are however significant differences between the concentrations of SiO2, TiO2, MgO, Ba, Sr, Nb and LREE between the ice core glass and the Minoan eruption, such that they cannot be correlatives. New chemical analyses of tephra from the Late Holocene eruption of the Aniakchak Volcano in Alaska, however, show a remarkable similarity to the ice core glass for all elements, and this eruption is proposed as the most likely source of the glass in the GRIP ice core. This provides a precise date of 1645 BC for the eruption of Aniakchak and is the first firm identification of Alaskan tephra in the Greenland ice cores. The age of the Minoan eruption of Santorini, however, remains unresolved.

Oh, okay, it wasn't in the Antarctic ice, it was in ocean floor sediments.

Ocean splashdown
by Henry Gee
UC Davis Geology Department
An asteroid between one and four km in diameter that splashed into the Southern Ocean, 1500 km SW of Chile, just over two million years ago, may have worsened a period of global cooling that saw the emergence of modern humans... The impact in question was first discovered during a cruise of the Eltanin in the 1960s: betrayed by anomalously high amounts of iridium in ocean-bed cores... Gersonde and his colleagues have taken another look, their results coming from a cruise in 1995 by the research ship Polarstern. The impact left a distinctive 'signature' of geological layers, very like that of the Chicxulub impact. Lowest in the 'impact' sequence is a thick layer of disordered rubble, full of chunks of rock up to 50 cm across: this layer represents the large-scale disturbance immediately after the impact as the ten-megaton blast ripped up the ocean floor. This layer took around four hours to settle after the blast. Smaller particles, such as grains of sand, took longer to settle, explaining why this layer was found immediately above the rubble layer. Capping the whole sequence is a thin layer of very fine sediment, dispersed over a wide area. This would have contained fine-grained material (including vaporized asteroid) flung high into the air and which took days or months to settle out. This layer contained the iridium.