Seasonal temperature changes obtained from carbonate clumped isotopes of annually laminated tufas from Japan: Discrepancy between natural and synthetic calcites
Seasonal temperature changes obtained from carbonate clumped isotopes of annually laminated tufas from Japan: Discrepancy between natural and synthetic calcites
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DOI：
10.1016/j.gca.2018.10.016
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发表时间：
2019
影响因子：
5
通讯作者：
H. Kato;Shota Amekawa;A. Kano;Taiki Mori;Y. Kuwahara;J. Quade
中科院分区：
文献类型：
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作者：
H. Kato;Shota Amekawa;A. Kano;Taiki Mori;Y. Kuwahara;J. Quade
碳酸盐凝聚同位素提供了一种新的古温度计，不需要环境水的同位素组成的知识。尽管付出了相当大的努力，实验室之间在聚集同位素（Δ 47）的丰度异常和绝对温度之间的经验校准方面存在着重大分歧，并且在天然样品的古温度估计中存在差异。在这项研究中，使用两种类型的17 O校正的聚集同位素分析的两个样品集的合成方解石和凝灰岩每月从两个地点在日本西南部与已知的δ 18 O值和温度的母水。这些测量结果构成了两个新的碳酸盐聚集同位素温度校准的基础，第一个来自日本九州大学实验室。在4个不同温度（2.9 ~ 6 1.0 ° C）下合成的方解石，其温度-Δ 47关系为Δ 47= 0.0 35 4 ± 0.0 0 13 × 10 6/T2 + 0.2 90 ± 0.0 15（R2 = 0.986），与近年来其他高温（70 ~ 10 0 ° C）酸溶实验的标定结果没有区别。天然石灰华样品的Δ 47测温比δ 18 O测温更能反映水温的季节变化。然而，在5.6 ~ 16.0° C温度范围内沉积的凝灰岩样品的Δ 47值低于用人造方解石标定的预期值，因此提供了另一个温度标定Δ 47= 0.0336±0.0036× 106/T2 + 0.301±0.048（R2 = 0.735）。因此，我们的结果清楚地确定了合成方解石和天然样品（凝灰岩）之间Δ 47温度校准的可检测但相当均匀的差异。凝灰岩和人工合成样品之间的Δ 47偏移幅度似乎与水温的季节变化和水的化学性质（包括pH、pCO 2和方解石的沉淀速率）无关。较低的Δ 47值以前曾在其他凝灰岩和凝灰岩中报道过，因此似乎与凝灰岩和凝灰岩固有的过程有关，如CO2脱气。我们还发现，我们的结果是不显着的影响，类型的17 O校正和几乎独立的散装同位素组成。
Carbonate clumped isotopes provide a novel paleo-thermometer that does not require knowledge of the isotopic compositions of environmental water. Despite considerable effort, there are substantial inter-laboratory disagreements in empirical calibrations between the abundance anomaly of the clumped isotopes (Δ 47) and absolute temperature, and discrepancies in paleo-temperature estimates from natural samples. In this study, clumped isotopes using two types of 17 O corrections were analyzed for two sample sets of synthetic calcites and tufas collected monthly from two sites in southwest Japan with known δ 18 O values and temperatures of parent water. These measurements form the basis for two new temperature calibrations of carbonate clumped isotopes, the first from our Kyushu University laboratory in Japan. The calcites synthesized at four different temperatures (2.9–61.0° C) yield a temperature-Δ 47 relationship of Δ 47= 0.0354±0.0013× 10 6/T 2+ 0.290±0.015 (R 2= 0.986), which is indistinguishable from the calibrations of other recent studies based on acid digestion experiments at high temperature (70–100° C). The Δ 47 thermometry for the natural tufa samples display the seasonal pattern of water temperature better than the δ 18 O thermometry. However, the Δ 47 values of the tufa samples deposited at temperatures ranging from 5.6 to 16.0° C were lower than the values expected from the calibration using synthetic calcites, thus providing another temperature calibration of Δ 47= 0.0336±0.0036× 10 6/T 2+ 0.301±0.048 (R 2= 0.735). Therefore, our results clearly identify a detectable, but fairly uniform, discrepancy in Δ 47-temperature calibration between synthetic calcite and natural samples (tufas). The amplitude of Δ 47 offset between the tufa and synthetic samples appears to be independent of the seasonal change in water temperature and the chemical properties of water, including pH, pCO 2, and precipitation rate of calcite. The lower Δ 47 values have been previously reported from other tufas and travertines, and therefore appear to be associated with processes inherent to tufas and travertines, such as CO 2 degassing. We also find that our results are insignificantly influenced by types of 17 O corrections and almost independent with bulk isotopic composition.