Cryo-paleosols and paleoclimate/cosmic archives in the Dry Valleys, Antarctica

Abstract

Perhaps the most obscure and overlooked paleoenvironmental resource in Antarctica is the cryosol-paleosol record of the Dry Valleys, and the cryo-stratigraphy of the Palmer Peninsula, East Antarctica, and the islands. The Scientific Committee on Antarctic Research (SCAR) Committee in 2014 outlined a forward look for new initiatives and of the six priorities, the ‘Reveal Antarctica’s History’ focused on ‘rock and sediment records to know whether past climate states are fated to be repeated’. Of all the records available to us across the continent, the thinnest and most obscure, are found within cryo-paleosols and accompanying clastic rinds, the latter often embedded in pavements capping these ancient sentinels. An ancient pedostratigraphy, extending horizon group-to-horizon group reported here, offers unexpectedly strong post-∼15 Ma weathering and salt accumulation, interrupted by a recent airburst, presumably the BM (black mat) of 12.8 ka. Evidence for a cosmic event comes in the form of melted/welded, air-quenched, dendritic, Pt (Ir) coated, organic-fused grains and highly sheaved and plate-uplifted mineral surfaces. As shown here, Antarctic paleosols, housing both oxidized and Na-encrusted beds, shed light not only on paleoclimatic/ecologic histories that might be repeated, but this one cometary occurrence, reported for the first time in any Dry Valley paleosols, may well occur again, the next time with enough energy to destroy Earth’s atmosphere.