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

古大气二氧化碳、古气候和低温铁(III)氧化物的稳定同位素地球化学地质记录表明，地球上的气候变化在广泛的时间和空间尺度上发生。因此，寻找气候变化因果关系问题的答案变得更加复杂。要深入了解通过地球流体圈(大气层和水圈)连接自然系统的机制，需要有关现代和古代环境的新信息来源。这些要求包括关于古代大气组成、地表温度和水循环行为的数据。对常见的低温氧化氢氧化铁、针铁矿(-FeOOH)的氧和氢同位素体系的研究已经确立了其作为关于潮湿、氧化的大陆环境(如红壤)的信息来源的价值。此外，还发现针铁矿在固溶体中以Fe(CO3)OH组分的形式存在于晶体结构中的少量CO2。这种Fe(CO3)OH可作为针铁矿结晶时存在的二氧化碳的分压和碳同位素组成的代表。因此，来自古代土壤的针铁矿可以用来确定水的同位素组成、古温度、古代生物活动的存在、土壤二氧化碳压力，以及在适当的情况下地球大气中的二氧化碳分压。本文建议继续努力，为显生宙期间大陆气候和大气化学的长期变化提供信息。两种古土壤(古新世晚期和始新世中期红土)支撑着早第三纪最高温度，已被确定为有希望进行研究的候选对象。碳、氢、氧同位素、化学、X射线衍射和岩石学数据将从这些高度淋溶的土壤的多个样本中获得。这些数据应提供有关大气二氧化碳压力、气候温度、水的同位素组成和生物活动的信息。

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.