Siderite 'clumped' isotope thermometry: A new paleoclimate proxy for humid continental environments
Siderite 'clumped' isotope thermometry: A new paleoclimate proxy for humid continental environments
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DOI：
10.1016/j.gca.2013.11.006
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发表时间：
2014-02-01
影响因子：
5
通讯作者：
Rosenheim, Brad E.
中科院分区：
文献类型：
--
作者：
Fernandez, Alvaro;Tang, Jianwu;Rosenheim, Brad E.
块状同位素测量可用于开发成土菱铁矿（FeCO3）的古气候潜力；然而，这种方法的适用性受到方解石和文石以外的矿物学缺乏团块同位素校准的限制。在这里，我们提出了在21到51摄氏度之间的实验室中生长的菱铁矿的无机校准。Delta（47）值和温度（10(6)/T-2， K）的线性回归产生以下关系（r(2) = 0.997）：Delta(47- rf) = (0.0356 +/- 0.0018) x 10(6)/T-2 +(0.172 +/- 0.019)我们证明，在当前的分析精度水平下，这种校准与方解石是无法区分的。我们的观察结果表明，两种不同碳酸盐矿物的块状同位素酸分选因子可能没有大的系统偏差。我们还介绍了从密西西比河三角洲全新世沉积物中收集的天然菱铁矿的块状同位素测量。我们发现菱铁矿记录了温暖季节的沼泽水温，而不是长期以来假定的年平均温度。这一发现对菱铁矿稳定同位素和团块同位素气候重建的准确性具有重要意义。(C) 2013 Elsevier Ltd.版权所有。
Clumped isotope measurements can be used to exploit the paleoclimatic potential of pedogenic siderite (FeCO3); however, the applicability of this method is held back by the lack of clumped isotope calibrations of mineralogies other than calcite and aragonite. Here we present an inorganic calibration of siderites grown in the laboratory between 21 and 51 degrees C. Linear regression of Delta(47) values and temperature (10(6)/T-2, K) yields the following relationship (r(2) = 0.997):Delta(47-RF) = (0.0356 +/- 0.0018) x 10(6)/T-2 + (0.172 +/- 0.019)We demonstrate that this calibration is indistinguishable from calcite at current levels of analytical precision. Our observations suggest that there is likely no large systematic bias in the clumped isotope acid fractionation factors between the two different carbonate minerals. We also present clumped isotope measurements of a natural siderite collected from Holocene sediments of the Mississippi River Delta. We find that siderites record warm season marsh water temperatures instead of mean annual temperatures as it has long been presumed. This finding has important implications for the accuracy of siderite stable isotope and clumped isotope based climate reconstructions. (C) 2013 Elsevier Ltd. All rights reserved.