The Impact of Late Eocene/ Early Oligocene Climate Change on the Continental Biota of Patagonia

始新世末渐新世初标志着世界气候从“温室”向“冰窖”转变的重要变化。在北美、欧洲和亚洲的大陆记录中已经研究了这种变化的时间和生物影响，它们显示出对当地和全球影响的反应。然而，到目前为止，还没有研究过南半球大陆哺乳动物和植物的序列。最近对巴塔哥尼亚岩石单元和生物群年龄的修正表明，阿根廷巴塔哥尼亚Gran Barranca的sammiento组跨越始新世晚期至渐新世早期；这是迄今为止在南半球发现的唯一跨越这一区间的大陆脊椎动物和植物序列。对食草哺乳动物的初步分析表明，剧烈的变化发生在相对较短的地质时间间隔内。同一沉积层间含有植物微化石，记录了植物群落的重要变化。该提案要求为进一步研究这种陆地生物变化提供资金。Gran Barranca的sammiento Fm的地质年代学将使用放射性测年法、tephra的化学鉴定和古磁学来改进。地层控制的收集将由脊椎动物和植物微化石组成。评估气候变化及其对生物群的影响：1)记录哺乳动物群落结构的变化（丰富度、起源和灭绝率以及生态形态）；2)通过植物岩研究记录植被和植物组成的变化。

AbstractThe end of the Eocene and the beginning of the Oligocene mark an important change in world climate, when it transitioned from 'greenhouse' to 'icehouse'. The timing and biotic impact of the change has been studied in the continental records of North America, Europe and Asia and they show a response to both local and global influences. As yet, however, no continental mammal and plant sequence has been studied in the Southern Hemisphere. Recent revision of the ages of rock units and biotas in Patagonia has demonstrated that the Sarmiento Fm at Gran Barranca in Patagonian Argentina spans the late Eocene through early Oligocene interval; this is the only known continental vertebrate and plant sequence so far identified from the Southern Hemisphere that spans this interval. Preliminary analysis of the mammalian herbivores suggests that dramatic changes occurred over a comparatively short interval of geologic time. The same sedimentary interval contains plant microfossils that document important change in the plant communities. This proposal requests funding for further study of this terrestrial biotic change. The geochronology of the Sarmiento Fm at Gran Barranca will be refined using radiometric dating, chemical identification of tephra, and paleomagnetism. Stratigraphically-controlled collections will be made of vertebrates and plant microfossils. Climate change and its impact on the biota will be assessed 1) by documenting changes in mammalian community structure (richness, origination and extinction rates and ecological morphology); and 2) by documenting changes in vegetation and floral composition from the study of phytoliths.