Neogene Palynology from Antarctic Marine and Glacial Sediments

该奖项支持使用耕层和海洋沉积物的孢粉学对横贯北极山脉的晚新生代植被进行研究。南极自大约40 Ma(Ma=距今100万年前)冰川开始以来的陆地植被记录鲜为人知。它被认为是在晚渐新世冰川作用(30 Ma)时被驱逐出南极的，并在中新世中期(15 Ma)肯定消失了。然而，保存完好的Nothofagus(南部山毛榉)的树枝、叶、根和花粉以及针叶花粉现在在横贯北极山脉的上新世中新世天狼星群(南纬86 oS；海拔1800米)中被发现。至少在上新世晚期才能存活下来，这意味着新近纪的气候比今天高出150到20摄氏度，即使在冰川时期也是如此。根据一种解释，现代寒冷极地气候的开始、植物的丧失和现代冰盖的生长都发生在过去3 Ma内。如果这些要求夏季平均气温高于5摄氏度的植物生长在横跨北极山脉的高海拔(1500米)上，那么茂盛的植被应该生长在海平面上，这应该在上新世海岸沉积物中产生丰富的花粉记录。这项研究的目的是了解大陆晚新生代的植被历史，从而约束南极冰盖历史的模型，并解决南半球上新世变暖的问题。

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.