Accelerator 14-C Dating of Individual Species of Small Animals for Reconstructing Paleoclimates 20,000-8000 Yr in N. America

来自北美的晚更新世小型哺乳动物动物群在过去20,000年中被广泛用作气候变化的代用品。这些更新世生物群的主要特征是其高度的物种多样性，存在非模拟群落(不和谐的动物群)，以及物种对区域气候变化的个体反应。由于不和谐动物群的概念对模拟气候变化和生物群落的发展至关重要，因此必须对这一假设进行定量检验-通过对目前异地分布的单个化石物种进行加速器质谱仪(AMS)C测年。目标是对沿着环境样带的三个分层洞穴的140个化石进行AMS C年代测定：德克萨斯州的霍尔洞穴、阿肯色州的佩卡里洞穴和田纳西州的贝克布拉夫洞穴。此外，来自单一成分遗址的大约20对不和谐的化石物种将被添加到数据集。C年代将1)评估不和谐的组合是否是自然发生的，2)提供物种迁徙的年表，3)显著改善过去20,000年的生物变化的年表。最终，C测年将提供动物群变化背景水平的定量数据--生态学家目前无法获得这些数据。

Late Pleistocene small mammal faunas from North America are used extensively as proxies for climate changes during the last 20,000 years. The dominant characteristic regarding these Pleistocene biotas is their high species diversity, the existence of non-analog communities (disharmonious faunas), and the individualistic response of species to regional climate change. Because the concept of disharmonious faunas is critical to modeling climate change and the development of biotic communities, this hypothesis must be tested quantitatively---by accelerator mass spectrometry (AMS) C dating of individual fossil species that are now allopatric. The goal is to AMS C date 140 fossils from three stratified caves along an environmental transect: Hall's Cave, Texas; Peccary Cave, Arkansas; and Baker Bluff Cave, Tennessee. In addition, approximately 20 pairs of disharmonious fossil species from single-component sites will be added to the data set. The C dates will 1) evaluate if disharmonious assemblages are natural occurrences, 2) provide chronologies for species migrations and 3) will improve significantly the chronologies for biotic changes during the past 20,000 years. Ultimately, the C dating will provide quantitative data on background levels of faunal change-- data presently unavailable to ecologists.