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

全球变化：始新世晚期到中新世大陆古气候的记录：马牙釉质磷酸盐的稳定同位素地球化学

• 批准号: 9219108
• 负责人: Philip Froelich
• 金额: $ 14.01万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1993
• 资助国家: 美国
• 起止时间: 1993-01-15 至 1995-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9219108&HistoricalAwards=false
• 关键词: Global; Change; Record; Late; Eocene

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.

我们将根据福塞尔马牙釉质磷酸盐的氧同位素组成重建晚始新世至中新世的大陆性气候。这段时间是全球气候恶化的重要时期，从古海洋学数据推断，大陆缺乏定量的地球化学信息。哺乳动物的18O磷灰石与体内的水平衡地沉淀，这反映了摄入的水。哺乳动物的体温是恒定的，因此18OPO4记录了受全球水文循环支配的当地水源的18O。化石珐琅的18OPO4可能记录了大陆古气候。木马化石是理想的，因为它们在地理上分布广泛，从始新世到晚更新世都很常见，并且有现代的类似物。我们将测定现代马牙齿、身体水和摄入水之间的同位素分馏，以定量重建化石马摄入水的18O。我们将确定牙齿化石中是否保存了大陆性气候信号；大陆性气候是否在幅度、方向和时间上反映了海洋记录；以及等量进化变化是否与大陆性气候变化同时发生。我们将分析怀俄明州、南达科他州和内布拉斯加州的化石，这些地方可以获得化石样本，众所周知的区域地层和年代学，以及靠近大陆中心的位置有利于气候研究。我们的初步数据表明，大多数釉质样本都保留了主要信号，可以检测到成岩作用。我们将进一步制定用红外、X射线衍射和元素分析评价成岩作用的标准。如果成岩作用可以忽略不计，我们将从18O古降水建立晚始新世至中新世古气候的定量记录。