Enhancing the Fidelity of Early Paleogene Planktic Foraminiferal Oxygen Isotope and Mg/Ca Records with the Use of In Situ Analytical Techniques

为继续发展和测试一项新技术提供资金，以便从保存在深海沉积物中的浮游生物壳中获得可靠的三角洲18O数据。该技术使用次级离子质谱仪（SIMS）对从早古近纪深海记录中恢复的单个浮游生物壳内的域进行原位三角洲18O分析。初步结果证实了这种方法的准确性，表明它将对量化和规避从浮游生物壳中获得的成岩作用对18O的影响产生革命性的影响。配对的δ 18O值与Mg/Ca比值将用于重建热带（Site 865）和亚极地（Site 690）纬度的早古近纪海温和海水δ 18O的变化。其腔壁上的脓疱生长（muricae）的基部区域代表了增强的生物钙化域，其中不包含壁上的孔隙，使其不易受到成岩作用的影响，是SIMS的理想目标。本研究的目的有三个：(1)重新评估早古近纪热带开放海洋海温。(2)量化成岩作用对古海洋代用物的影响。(3)比较低纬度和高纬度记录，重点关注瞬态高温气候状态。更广泛的影响：当该方法被广泛应用时，可能会改变基于浮游有孔虫三角洲18O的古气候研究。早古近纪温室气候的研究可以作为未来由化石燃料排放驱动的气候变化的模拟。

Funds are provided for the continued development and testing of a new technique for acquiring reliable delta 18O data from slightly to moderately altered planktic shells preserved in deep-sea sediments. This technique uses a secondary ion mass spectrometer (SIMS) for in situ delta 18O analysis of domains within individual planktic shells recovered from Early Paleogene deep-sea records. Initial results confirm the veracity of this approach suggesting that it will be transformative for quantifying and circumventing the effects of diagenesis on 18O obtained from planktic shells. Paired delta 18O values with Mg/Ca ratios in the same planktic shell will be used to reconstruct Early Paleogene variation in SSTs and seawater delta 18O at tropical (Site 865) and subpolar (Site 690) latitudes. The basal areas of pustular outgrowths (muricae) on their chamber walls represent domains of enhanced biocalcification that contain no mural pores, making them less susceptible to diagenesis and ideal targets for SIMS. Objectives of this proposal are threefold: (1) Reassess tropical open-ocean SSTs during the Early Paleogene. (2) Quantify the effects of diagenesis on paleoceanographic proxies. (3) Compare low- and high-latitude records with emphasis on transient hyperthermal climate states.Broader Impacts: The method, when widely applicable, could transform the study of paleoclimates based of planktic foraminiferal delta 18O. The study of Early Paleogene greenhouse climate could be an analog for future climate change driven by fossil fuel emissions.