Collaborative Research: Actualistic Calibration of the Sphaerosiderite Paleoclimate Proxy

拟议的研究涉及对成土菱铁矿形成的现代遗址进行经验性、现实性研究的需要，这些研究可以检验球铁菱铁矿古气候指标原始公式中使用的简化假设。球状菱铁矿替代物目前正被用于验证地球历史上过去暖期的一般环流模型模拟(与NSF-ATM计划中的其他人合作研究)，拟议的研究将减少该地球化学代理人应用的不确定性。拟议的研究将在选定的现代成壤菱铁矿形成地点进行野外调查，将涉及：(1)采样土壤的野外和实验室特征；(2)采样的现代成壤菱铁矿的稳定同位素分析；(3)地下水中菱铁矿、土壤有机质和溶解无机碳的放射性碳测年；(4)现场和实验室现场地质微生物学和地下水化学特征，以了解与菱铁矿形成相关的低温过程和稳定同位素分馏。建议对德克萨斯州东部和路易斯安那州美国墨西哥湾沿岸的现代水相土壤以及新泽西州南部半干旱地区的沼泽铁矿进行现场调查。此次调查的更广泛影响将包括改善贝勒大学和堪萨斯大学未被充分代表的群体的研究生和本科生的研究培训机会。这项研究的科学价值将包括：(1)现代淡水菱铁矿形成的文献和精确年代测定；(2)密切研究降水的氧同位素组成(Delta18O)与美国东部形成菱铁矿的沿海站地下水Delta18O值之间的关系；(3)经验地确定了几个已发表的菱铁矿-水18O分馏方程中在一定沉积温度范围内最合适的分馏方程；(4)提高了对自然环境中低温菱铁矿形成所涉及的生物地球化学过程的理解；(5)发展了改进的经验基础，将球菱铁矿古气候指标应用于目前正在开发的地球历史暖期的大气环流模式模拟(在NSF-ATM计划中)，从而促进了基础大气研究。

The proposed research addresses a need for empirical, actualistic studies of modern sites of pedogenic siderite formation that can test the simplifying assumptions that were used in the original formulation of the sphaerosiderite paleoclimate proxy. The sphaerosiderite proxy is now being used for validation of General Circulation Model simulations of past warm periods in Earth History (collaborative research by others in the NSF-ATM program), and the proposed research would reduce uncertainties in the application of this geochemical proxy.The proposed research will carry out field investigations at selected sites where modern pedogenic siderite is forming, and will involve: (1) field and laboratory characterizations of sampled soils; 2) stable isotopic analyses of sampled modern pedogenic siderites; (3) radiocarbon dating of the siderite, soil organic matter, and dissolved inorganic carbon in the groundwater; (4) field and laboratory characterizations of the in situ geomicrobiology and groundwater chemistry to understand the low temperature processes and stable isotope fractionations related to siderite formation.Field investigations of modern hydromorphic soils are proposed along the U.S. Gulf coast in eastern Texas and Louisiana, and in the bog iron ores of the pinelands of southern New Jersey. Selected sites were chosen because of earlier reports of recent siderite formation, or because they are closely analogous to other sites of siderite formation.The broader impacts of this investigation will include improvements in the research training opportunities for graduate and undergraduate students from underrepresented groups at both Baylor University and the University of Kansas.The scientific merits of this study will include: (1) Documentation and precise dating of modern fresh water siderite formation; (2) Close examination of the relationship between the oxygen isotope composition (delta18O) of precipitation and groundwater delta18O values in coastal stations in the eastern United States where siderite is forming; (3) Empirical determination of the most appropriate of several published siderite-water 18O fractionation equations over a range of sedimentary temperatures; (4) Improved understanding of the biogeochemical processes involved in low-temperature siderite formation in natural environments; (5) Development of an improved empirical foundation for application of the sphaerosiderite paleoclimate proxy to currently developing general circulation model simulations of warm periods in Earth History (in NSF-ATM program), thereby advancing basic atmospheric research.