Triple oxygen isotopes in biogenic and sedimentary carbonates
Triple oxygen isotopes in biogenic and sedimentary carbonates
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DOI：
10.1016/j.gca.2014.06.006
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发表时间：
2014-09-15
影响因子：
5
通讯作者：
Levin, Naomi E.
中科院分区：
文献类型：
--
作者：
Passey, Benjamin H.;Hu, Huanting;Levin, Naomi E.
天然沃茨的O-17异常（Delta O-17）已被证明对蒸发敏感，其方式类似于氘过量，具有蒸发的水体（例如，叶沃茨、湖泊沃茨、动物体沃茨）的δ O-17往往低于原始大气沃茨。在动物体内的水中，Delta O-17与蒸发沃茨的摄入量、水的蒸发流出量和大气O-2的Delta O-17值有关，大气O-2本身携带着全球碳循环和平流层光化学反应的特征。碳酸盐岩具有记录母沃茨的三重氧同位素组成的潜力，可以重建过去的水组成，但这种调查一直在等待开发高精度测量碳酸盐岩的Delta O-17的方法。我们描述了基于顺序酸消化/还原/重结晶方法的优化方法，该方法产生具有高精度（类似于0.010千分之一，1西格玛）的Delta O-17数据，以解决微妙的环境信号。我们报告了第一个高精度的Delta O-17陆地碳酸盐数据集，重点是脊椎动物生物碳酸盐和土壤碳酸盐，但也包括海洋无脊椎动物和高温碳酸盐。我们确定了碳酸盐和碳酸盐的母沃茨之间的O-2分析物的明显的三同位素分馏因子。这些与适当的温度估计值（从聚集的同位素测温法，或已知或估计的体温）相结合，用于计算母沃茨的δ O-18和δ O-17。出现的最清晰的模式是鸟类、哺乳动物和哺乳动物体内水（来自蛋壳和牙釉质的分析）相对于大气沃茨的O-17-消耗强烈，遵循蒸发水的预期影响（例如，叶水）和大气O-2对脊椎动物体内水的影响。这里研究的土壤碳酸盐的母质沃茨具有类似于或略低于全球降水的Delta O-17值。我们的研究结果表明，三角洲O-17将有有益的应用，古环境研究的大陆环境中，蒸发的影响是重要的，脊椎动物体内的水可能会记录蒸发的水源和大气中的氧的同位素信号。(C)2014爱思唯尔有限公司版权所有。
The O-17 anomaly (Delta O-17) of natural waters has been shown to be sensitive to evaporation in a way analogous to deuterium excess, with evaporated bodies of water (e.g., leaf waters, lake waters, animal body waters) tending to have lower Delta O-17 than primary meteoric waters. In animal body water, Delta O-17 relates to the intake of evaporated waters, evaporative effluxes of water, and the Delta O-17 value of atmospheric O-2, which itself carries signatures of global carbon cycling and photochemical reactions in the stratosphere. Carbonates have the potential to record the triple oxygen isotope compositions of parent waters, allowing reconstruction of past water compositions, but such investigations have awaited development of methods for high-precision measurement of Delta O-17 of carbonate. We describe optimized methods based on a sequential acid digestion/reduction/fluorination approach that yield Delta O-17 data with the high precision (similar to 0.010 parts per thousand, 1 sigma) needed to resolve subtle environmental signals. We report the first high-precision Delta O-17 dataset for terrestrial carbonates, focusing on vertebrate biogenic carbonates and soil carbonates, but also including marine invertebrates and high-temperature carbonates. We determine apparent three-isotope fractionation factors between the O-2 analyte derived from carbonate and the parent waters of the carbonate. These in combination with appropriate temperature estimates (from clumped isotope thermometry, or known or estimated body temperatures) are used to calculate the delta O-18 and Delta O-17 of parent waters. The clearest pattern to emerge is the strong O-17-depletion in avian, dinosaurian, and mammalian body water (from analyses of eggshell and tooth enamel) relative to meteoric waters, following expected influences of evaporated water (e.g., leaf water) and atmospheric O-2 on vertebrate body water. Parent waters of the soil carbonates studied here have Delta O-17 values that are similar to or slightly lower than global precipitation. Our results suggest that Delta O-17 will have useful application to paleoenvironmental studies of continental environments where the effects of evaporation are important, and where vertebrate body water may record an isotopic signal of evaporated water sources and atmospheric oxygen. (C) 2014 Elsevier Ltd. All rights reserved.