Neogene Palynology from Antarctic Marine and Glacial Sediments

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This award supports a study of late Cenozoic vegetation in the Transantarctic Mountains using palynology of tills and marine sediments. The record of terrestrial vegetation in Antarctica since the onset of glaciation at about 40 Ma (Ma = million years before present) is poorly known. It was thought to have been expelled from Antarctica during a late Oligocene glaciation (30 Ma), and certainly lost by middle Miocene time (15 Ma). However, well-preserved twigs, leaves, roots, and pollen of Nothofagus (southern beech) and coniferous pollen are now known from the mid- to upper Pliocene Sirius Group (86oS latitude; 1800m above sea level) in the Transantarctic Mountains. Nothofaguso survival until at least the late Pliocene implies a Neogene climate 15o to 20oC warmer than today, even during glacial periods. Based on one interpretation, onset of the present cold polar climate, loss of the plants, and growth of the present ice sheet all occurred within the last 3 Ma. If the plants, which require mean summer temperatures warmer than 5oC, grew at high elevations (1500m) in the Transantarctic Mountains, then a lush vegetation should have grown at sea-level which should have produced a rich pollen record in Pliocene coastal sediments. The goals of this study are to understand the late Cenozoic vegetation history of the continent and thereby to constrain models for the history of the Antarctic ice sheets and to resolve the question of Pliocene warming in the southern hemisphere.