SGER:A test for modern carbon in Paleozoic paleosols

摘要：该项目将测试在威斯康星州内达和爱荷华州内达的上奥陶统内达组古土壤中发现的针铁矿中现代碳的存在。导致我们认为这些沉积物中可能存在活碳（14C）的因素包括测量氢氧化物土壤矿物中封闭碳的技术的发展以及内达组沉积后蚀变的想法。该测试的结果将对古二氧化碳分压代理工作和建模的可靠性产生重要影响。如果发现了现代碳，那么这必须与以前工作的所有假设相一致。如果没有发现现代的碳，那么这就给以前所有工作的假设增加了可信度。后勤工作包括：(1)在内华达州、威斯康星州和爱荷华州的不同地点对古土壤铁石进行短暂的实地考察，(2)使用完善的化学/热衰减协议从针铁矿中提取碳，以及(3)对所有相关碳相的12C、13C和14C进行同位素测量。实验室工作将在乔治亚大学地质系稳定同位素实验室和应用同位素光谱学AMS设施中心进行。资金将用于(1)收集样本和展示结果的旅行，(2)同位素质谱分析，以及(3)为一年级博士生提供暑期助教。智力优势：本研究结合了最近发现的土壤矿物中的现代碳闭塞，以及古代古土壤在暴露于近地表风化时可能经历再结晶的观点。所提出的活动产生的更广泛的影响：如果发现了现代碳，那么这必须与以前的古二氧化碳分压代理工作和建模的所有假设相一致。

ABSTRACTThis 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.