Radiocarbon (14C) dating of sediment deposition around Antarctica is often challenging due to heterogeneity in sources and ages of organic carbon in the sediment. Chemical and thermochemical techniques have been used to separate organic carbon when microfossils are not present. These techniques generally improve on bulk sediment dates, but they necessitate assumptions about the age spectra of specific molecules or compound classes and about the chemical heterogeneity of thermochemical separations. To address this, the Rafter Radiocarbon Laboratory has established parallel ramped pyrolysis oxidation (RPO) and ramped pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) systems to thermochemically separate distinct carbon fractions, diagnose the chemical composition of each fraction, and target suitable RPO fractions for radiocarbon dating. Three case studies of sediment taken from locations around Antarctica are presented to demonstrate the implementation of combined RPO-AMS and Py-GC-MS to provide more robust age determination in detrital sediment stratigraphy. These three depositional environments are good examples of analytical and interpretive challenges related to oceanographic conditions, carbon sources, and other factors. Using parallel RPO-AMS and Py-GC-MS analyses, we reduce the number of radiocarbon measurements required, minimize run times, provide context for unexpected 14C ages, and better support interpretations of radiocarbon measurements in the context of environmental reconstruction.

中文翻译：

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通过组合斜坡热解氧化和热解-GC-MS 推进南极沉积年代学

放射性碳（14C）由于沉积物中有机碳的来源和年龄的异质性，对南极洲周围沉积物沉积的测年通常具有挑战性。当微化石不存在时，化学和热化学技术已被用来分离有机碳。这些技术通常会改进大量沉积物的年代，但它们需要对特定分子或化合物类别的年龄谱以及热化学分离的化学异质性进行假设。为了解决这个问题，拉夫特放射性碳实验室建立了并行斜坡热解氧化 (RPO) 和斜坡热解-气相色谱-质谱 (Py-GC-MS) 系统，以热化学方式分离不同的碳组分，诊断每个组分的化学成分，并确定适合放射性碳测年的 RPO 分数。介绍了从南极洲周围地区采集的沉积物的三个案例研究，以证明 RPO-AMS 和 Py-GC-MS 组合的实施，以在碎屑沉积物地层学中提供更可靠的年龄确定。这三种沉积环境是与海洋条件、碳源和其他因素相关的分析和解释挑战的好例子。使用并行 RPO-AMS 和 Py-GC-MS 分析，我们减少了所需的放射性碳测量数量，最大限度地缩短了运行时间，为意外情况提供了背景信息14C年龄，并更好地支持环境重建背景下放射性碳测量的解释。