This project will test for the presence of modern carbon in goethite found in paleosols of the Upper Ordovician Neda Formation, in Neda, Wisconsin and Iowa. Factors that lead us to think there may be live carbon (14C) in these deposits include the development of the technology to measure carbon occluded in hydroxide soil minerals and the idea that post-depositional alteration of the Neda Formation has occurred. The outcome of this test will have important ramifications for the reliability of paleo-PCO2 proxy work and modeling. If modern carbon is found, then this must be reconciled with all the assumptions of previous work. If modern carbon is not found, then this gives added credence to assumptions of all previous work.
Logistics involve (1) a short field expedition to sample paleosol ironstone in various locations in Neda, Wisconsin and Iowa, (2) extraction of the carbon from goethite using well established chemical/thermal decrepitating protocols, and (3) isotopic measurement of 12C, 13C, and 14C of all associated carbon phases. Laboratory work will be conducted at the University of Georgia Department of Geology Stable Isotope Laboratory and the Center for Applied Isotope Spectroscopy AMS facility. Funds will be used for (1) travel to collect samples and present results, (2) isotope mass spectrometry, and (3) a summer assistantship for a first-year Ph.D. student.
Intellectual merit: This study integrates the recent discovery of modern carbon occlusion in soil minerals with the idea that ancient paleosols may undergo recrystallization while exposed to near surface weathering. Broader impact resulting from proposed activity: If modern carbon is found, then this must be reconciled with all the assumptions of previous paleo-PCO2 proxy work and modeling.
