This paper examines a massive network of bedrock channels, some as much as 250 m (775 ft) deep and 600 m (1860 ft) wide, that sit at the head of Wright Valley in the Dry Valleys region of Antarctica. Since they were first observed in the 1950s, their age and origin has been a mystery. In this paper we provide evidence that huge subglacial floods cut the channels more than 12 million years ago. The age interpretation is based on ash deposits that rest on top of an erosion surface within the Labyrinth. An important implication is that erosion rates in the Dry Valleys are exceptionally low, and have been for millions of years, to preserve channel morphology. Meltwater associated with these flood events discharged to the Southern Ocean and may have influenced global climate during the Miocene.

Lewis, A.R., D.R. Marchant, D.E. Kowalewski, S.L. Baldwin, and L.E. Webb, 2006. The age and origin of the Labyrinth, western Dry Valleys, Antarctica: Evidence for extensive middle Miocene subglacial floods and freshwater discharge to the Southern Ocean. Geology, v. 34, p. 513-516.

This paper provides an overview of an extraordinarily well-preserved fossil assemblage discovered in the western Olympus Range. Download the pdf and supporting info here - also available free of change from PNAS website. The fossils, which include mosses, pollen, insects, ostracods, and diatoms, are preserved in lake sediments that formed where a small moraine trapped meltwater 14.07 million years ago. The life requirements of the organisms mean that summer temperatures averaged at least 5 C, but the glacial record shows that shortly afterward climate had cooled to the point where glaciers no longer produced melt water, even during the summer. The lack of water combined with the extreme cold most likely drove the organisms to extinction by 13.85 million years ago.

Lewis, A.R., D.R. Marchant, A.C. Ashworth, L. Hedenas, S.R. Hemming, J.V. Johnson, M.J. Leng, M.L. Machlus, A.E. Newton, J.I. Raine, J.K. Willenbring, and A.P. Wolfe, 2008, Mid-Miocene cooling and the extinction of tundra in continental Antactica. Poc Nat Acad Sci, v. 105, n. 31, p. 10676-10680.

This paper details glacial evidence for a rapid, one-way shift in the thermal regimes of small alpine glaciers in the Transantarctic Mountains. The shift indicates that a significant climate cooling occurred in the Dry Valleys region 13.9 million years ago. Once climate had cooled, it never warmed again to the point that glaciers in the area regained surface melting zones or wet-based thermal regimes. The chronology is based on Ar/Ar dating of multiple ash layers within and between tills. The climate shift correlates nearly perfectly to a major reduction in sea-surface temperature reported for the Southern Ocean.

Lewis, A.R., D.R. Marchant, A.C. Ashworth, S.R. Hemming, and M.L. Machlus, 2007, Major middle Miocene global climate change: Evidence from East Antarctica and the Transantarctic Mountains. GSA Bulletin, v. 119, p. 1449-1461.