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

摘要始新世的结束和渐新世的开始，标志着世界气候发生了重大变化，从温室向冰室过渡。北美、欧洲和亚洲的大陆记录已经研究了这种变化的时间和生物影响，它们显示了对当地和全球影响的反应。然而，到目前为止，南半球还没有研究过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订表明，阿根廷巴塔哥尼亚Gran Barranca的Sarmiento FM跨越了始新世晚期至渐新世早期；这是迄今在南半球发现的唯一跨越这一时期的大陆脊椎动物和植物序列。对哺乳动物食草动物的初步分析表明，在相对较短的地质时间间隔内发生了戏剧性的变化。同一沉积间隔包含植物微体化石，它们记录了植物群落的重要变化。这项提案要求为进一步研究这种陆地生物变化提供资金。位于Gran Barranca的Sarmiento FM的地质年代学将通过放射性测年、特弗拉化学鉴定和古地磁进行精炼。地层学控制的收集将包括脊椎动物和植物微化石。将对气候变化及其对生物群的影响进行评估：1)通过记录哺乳动物群落结构的变化(丰富度、起源和消失率以及生态形态)；以及2)通过研究植物硅体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.