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.
