Global Change: A Record of Late Eocene to Miocene Continental Paleoclimate: Stable Isotope Geochemistry of Equid Enamel-Phosphate

我们将重建晚始新世至中新世的大陆性气候， 马牙釉质磷酸盐的氧同位素组成。 这段时间是全球气候变化的重要时期 根据古海洋学数据推断， 定量地球化学信息。 18O 哺乳动物的磷灰石在与身体水分平衡时沉淀， 这反映了摄入的水分。 哺乳动物的体温是 18 OPO 4记录了当地水源的18 O 这是由全球水文循环控制的。 18OPO4 化石珐琅可以记录大陆的古气候。 化石马科动物 是理想的，因为它们在地理上分布广泛， 始新世至更新世晚期，并有现代类似物。 我们将 确定牙齿、身体水分和 在现代马中摄入水以定量重建18 O 摄入的水的比例。 我们将确定是否 化石牙釉质中保存有大陆性气候信号; 如果大陆性气候反映了海洋性气候的规模， 方向和时间;如果平等的进化发生变化， 与大陆气候变化同时发生。 我们将分析 来自怀俄明州、南达科他州和内布拉斯加州的化石， 样品是可用的，区域地层和年代学是 众所周知，靠近大陆中心的位置是 有利于气候研究。 我们的初步数据显示 大多数釉质样品和成岩作用都保留了原始信号 可以被检测到。 我们将进一步制定评估标准， 岩作用 红外线，X射线衍射和元素分析 如果 成岩作用可以忽略不计，我们将开发一个定量记录， 古18 O以来晚始新世-中新世古气候 降水

We will reconstruct late eocene to Miocene continental climate from the oxygen isotopic composition of fossel equid enamel phosphate. This interval is an important period of global climatic deterioration inferred from paleoceanographic data with scant quantitative geochemical information from continents. The 18O mammalian apatite precipitates in equilibrium with body water, whcih reflects ingested water. Body temperature of mammals is constant and known so 18OPO4 records the 18O of local water sources which are dominated by the global hydrologic cycle. The 18OPO4 of fossil enamel may record continetal paleoclimate. Fossil equids are ideal because they are geographically widespread, common from the Eocene to late Pleistocne, and have modern analogues. We will determine the isotopic fractionation between teeth, body water, and ingested water in modern equids to quantitatively reconstruct 18O of ingested water for fossil equids. We will determine if a continental climatic signal is preserved in fossil tooth enamal; if continental climate reflects the marine record in magnitude, direction, and timing; and if equid evolutionary change occurred concurrently with continetal climatic change. We will analyze fossils from Wyoming, South Dakota, and Nebraska, where fossil samples are available, regional stratigraphy and chronology are well known, and location near the center of the continent is advantageous for climate studies. Our preliminary data indicate a primary signal is retained by most enamel samples and diagenesis can be detected. We will further develop criteria for evaluating diagenesis with infrared, XRD, and elemental analyses. If diagenesis is negligible, we will develop a quantitative record of late Eocene to Miocene paleoclimate from 18O of ancient precipitation.