High-Resolution Mammal Biostratigraphy and Response to Transient Climate Change at the Paleocene-Eocene Carbon Isotope Excursion

在距今5550万年前的古新世-始新世分界线与85，000年短暂气候变化的温室事件的突然发生相吻合，古新世-始新世热极大期或PETM，涉及从浅海甲烷储层向大气中释放大量轻碳。 由此产生的负碳同位素漂移（CIE）首先在深海中被发现，然后在怀俄明州的北方大角盆地的陆地上被发现。 在大角盆地，CIE与“Wa-0”动物群移民事件相吻合，包括第一次出现现代哺乳动物，如偶蹄目，奇蹄目和灵长类动物在北美，以及一些哺乳动物谱系的突然但短暂的缩小。 这里的研究涉及PETM间隔大陆哺乳动物的高分辨率生物地层学调查。 目前正在比格霍恩盆地和克拉克福克盆地边缘研究一个50米厚的地层剖面，其中包括CIE和Wa-0哺乳动物群。 具体目标包括：测量地层剖面，记录该区间的标志层和侧向相变;利用差分全球定位系统以米级精度绘制将剖面连接在一起的独特标志层;相对于测量和绘制的地层单元确定已知化石的位置;确定生产性新岩性的位置;量化穿过Wa-0区间的所有谱系的身体大小变化;准备和描述以前收集的Wa-0哺乳动物标本和新标本，重点是在Wa-0底部新发现的Meniscotherium priscum间隔;收集更多的区系标本（雀鳝鳞片，Coryphodon牙齿等）通过大陆CIE/Wa-0间隔进行氧同位素和古温度的高分辨率研究。 总体目标是更好地了解生物对短期气候变化的反应。

The Paleocene-Eocene epoch boundary at 55.5 million years before present coincides with the sudden onset of an 85,000-year greenhouse event of transient climate change, the Paleocene-Eocene thermal maximum or PETM, that involved release of massive amounts of light carbon into the atmosphere from shallow marine methane reservoirs. The resulting negative carbon isotope excursion [CIE] was first recognized in the deep sea, and then on land in the northern Bighorn Basin, Wyoming. In the Bighorn Basin the CIE coincides with a "Wa-0" faunal immigration event including the first appearance of modern orders of mammals such as Artiodactyla, Perissodactyla, and Primates in North America, and with an abrupt but short-lived diminution in size of some mammalian lineages. Research here involves high resolution biostratigraphic investigation of continental mammals in the PETM interval. A 50-m-thick stratigraphic section containing the CIE and Wa-0 mammalian fauna is being studied around the margin of the Bighorn and Clarks Fork basins. Specific objectives include measurement of stratigraphic sections documenting marker beds and lateral facies changes in this interval; mapping of distinctive marker beds tying sections together using differential GPS with meter-scale precision; location of known fossils relative to measured and mapped bed units; location of productive new lithologies; quantification of body size change in all lineages crossing the Wa-0 interval; preparation and description of previously collected and new specimens of Wa-0 mammals focusing on the newly-discovered Meniscotherium priscum interval at the base of Wa-0; and collection of additional faunal specimens (gar scales, Coryphodon teeth, etc.) of known bed level for high resolution study of oxygen isotopes and paleotemperature through the continental CIE/Wa-0 interval. The overall objective is better understanding of biotic response to short-term climate change.