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

已提供资金，继续开发和测试一种新技术，从深海沉积物中保存的轻微至中度蚀变的南极贝壳获取可靠的δ 18 O数据。该技术使用二次离子质谱仪（西姆斯）在现场三角洲18 O分析的域内的个别南极壳恢复从早第三纪深海记录。初步结果证实了这种方法的准确性，这表明它将是变革的量化和规避成岩作用的影响，18 O从南极壳。在相同的南极壳中，成对的三角洲18 O值与Mg/Ca比值将用于重建热带（865站）和副极地（690站）纬度的SST和海水三角洲18 O的早第三纪变化。脓疱增生物（muricae）在其室壁上的基底区域代表了不含壁孔的增强生物钙化的域，使其不易受成岩作用的影响，是西姆斯的理想目标。本研究的目的有三：（1）重新评估古近纪早期热带公海SST。(2)量化成岩作用对古海洋学指标的影响。(3)比较低纬度和高纬度记录，重点是短暂的高温气候状态。更广泛的影响：该方法，广泛适用时，可以改变古气候的研究基础上的南极有孔虫三角洲18 O。古近纪早期温室气候的研究可以模拟未来化石燃料排放驱动的气候变化。

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.