Ancient Atmospheric Carbon Dioxide, Paleoclimates, and the Stable Isotope Geochemistry of Low Temperature Iron (III) Oxides

古代大气二氧化碳、古气候和低温氧化铁 (III) 的稳定同位素地球化学

• 批准号: 0106257
• 负责人: Crayton Yapp
• 金额: $ 30.72万
• 依托单位: Southern Methodist University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-06-15 至 2005-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0106257&HistoricalAwards=false
• 关键词: Ancient; Atmospheric; Carbon; Dioxide; Paleoclimates

EAR-0606257Crayton J. YappAbstractAncient Atmospheric CO2, Paleoclimates, and the Stable Isotope Geochemistry of Low Temperature Iron (III) OxidesThe geologic record has revealed that climate change on Earth occurs on a wide range oftemporal and spatial scales. As a result, the search for answers to questions about causality in climate change has become more complex. Development of a deep understanding of the mechanisms by which natural systems were (and are) linked through the Earth's fluid spheres(the atmosphere and hydrosphere) requires new sources of information on both modern and ancient environments. Among the requirements are data on the composition of ancient atmospheres, surficial temperatures and the behavior of the hydrologic cycle.Studies of the oxygen and hydrogen isotope systematics of the common, low-temperatureiron oxyhydroxide, goethite ( -FeOOH), have established its value as a source of information on wet, oxidizing, continental environments such as lateritic soils. Moreover, it was discovered that a small amount of CO2 is istrapped in the crystal structure of goethite as an Fe(CO3 )OH component in solid solution. This Fe(CO3 )OH serves as a proxy for the partial pressure and carbon isotope composition of CO2 present at the time of goethite crystallization. Therefore, goethite from ancient soils can be used to determine the isotopic composition of waters, paleotemperatures, the presence of ancient biological activity, soil CO2 pressures, and, under the right circumstances, the partial pressure of CO2 in the Earth's atmosphere.A continuation of efforts to contribute information on long-term changes in continental climate and atmospheric chemistry during the Phanerozoic is proposed here. Two paleosols (Late Paleocene and Middle Eocene laterites) that bracket the Early Tertiary thermal maximum have been identified as promising candidates for study. Carbon,hydrogen and oxygen isotope, chemical, XRD and petrographic data would be obtained from multiple samples of these highly leached soils. These data should provide information on atmospheric CO2 pressures, climatic temperatures, isotopic compositions of waters and biological activity.

古大气CO2、古气候和低温氧化铁的稳定同位素地球化学地质记录表明，地球上的气候变化发生在广泛的时空尺度上。因此，寻找气候变化因果关系问题的答案变得更加复杂。要深入了解自然系统过去和现在通过地球的流体圈（大气圈和水圈）相互联系的机制，就需要有关于现代和古代环境的新的信息来源。这些要求包括古大气成分、地表温度和水文循环行为的数据。对常见的低温氢氧化铁、针铁矿（-FeOOH）的氧和氢同位素系统学的研究已经确立了它作为潮湿、氧化、大陆环境如红土的信息来源的价值。此外，还发现少量CO_2以Fe（CO_3）OH固溶体的形式存在于针铁矿的晶体结构中。这Fe（CO 3）OH作为一个代理的分压和碳同位素组成的CO2目前在针铁矿结晶的时间。因此，古土壤中的针铁矿可用于确定沃茨的同位素组成、古温度、古生物活动的存在、土壤CO2压力，以及在适当的条件下，地球大气中的CO2分压。两个古土壤（晚古新世和中始新世红土），括号中的早第三纪热最大已被确定为有前途的候选人进行研究。碳，氢和氧同位素，化学，XRD和岩相学数据将从这些高度沥滤土壤的多个样品中获得。这些数据应提供关于大气CO2压力、气候温度、沃茨的同位素组成和生物活动的资料。