Systematics and application of the carbonate 'clumped isotope'thermometer in foraminifera and coccoliths

研究表明，碳酸盐中的18O/16O （18O）和金属/钙比值，以及有机生物标志物的结构，可以用来定量估计温度和水的组成。然而，无机（18O, Mg/Ca）和有机（UK'37和TEX86）温度代用物对生物、生态和非温度环境因子的敏感性可能导致气候重建中的系统误差或模糊性。几乎所有的温度指标都受到“生命效应”和其他非温度环境参数的影响。大多数现有的代用物必须参考水的成分——使用有孔虫中的18O或Mg/Ca比率作为温度的代用物需要分别了解水的18O或Mg/Ca。这两种指标对碳酸盐离子浓度都比较敏感。此外，对于许多温度代用物（例如UK'37, TEX86, Mg/Ca），还没有详细的机制理解。所有这些因素都导致了对过去条件的解释的不确定性，特别是对于已灭绝的分类群，人们无法建立可靠的代理经验校准。一种可能不受这些限制的技术是新的碳酸盐“块状同位素”温度计。团块同位素测温法的原理是，重同位素在分子、矿物质或有机成分中排列或“团块”成键是一种温度依赖现象。在碳酸盐中，稀有的重同位素（13C, 18O）出现在丰富的轻同位素池中。根据统计热力学原理，预测碳酸盐矿物晶格中13C和18O相互结合的比例与温度有关。在实践中，碳酸盐团块同位素温度计是基于对碳酸盐岩酸消化产生的二氧化碳中的13C18O16O的分析。有了这个奖学金，我建议在浮游和底栖有孔虫和球岩体中开发碳酸盐“块状同位素”温度计的第一个校准。到目前为止，已经进行了有限数量的测量来校准？47在已知温度下沉淀的无机方解石（4个样本）、鱼耳石（8个样本）、软体动物（3个样本）、腕足动物（3个样本）和珊瑚（3个样本）中。目前还没有从培养的生物样本、详细的野外采样中验证块状同位素温度计，也没有对有孔虫和球岩石进行测量——所有这些都是古海洋学研究所必需的。除了在培养的有孔虫和球粒岩中校准这种新的同位素温度计外，我还将使用这些数据来测试18O和13C“生命效应”起源的模型。我还将把这个温度计应用到末次冰期最大值的样本上，这些样本来自热带太平洋西部的暖池。西太平洋暖池是最温暖的开放海洋区域，也是气候模型的基准。对该地区冰期-间冰期海面温度变化的重建在1 ~ 6°C之间，不同方法之间存在系统差异。最后，我将把这个温度计应用于来自南大洋的古新世-始新世边界样本，以限制与大量碳释放相关的变暖。

Research has shown that 18O/16O ( 18O) and metal/calcium ratios in carbonates, and the structure of organic biomarkers, can be used to give quantitative estimates of temperature and water composition. However, the sensitivity of inorganic ( 18O, Mg/Ca) and organic (UK'37 and TEX86) temperature proxies to biological, ecological, and non-temperature environmental factors can result in systematic errors or ambiguities in climate reconstructions. Almost all temperature proxies are subject to 'vital effects' and other non-temperature environmental parameters. Most existing proxies must be referenced to water composition - use of 18O or Mg/Ca ratios in foraminifera as a proxy for temperature requires knowledge of water 18O or Mg/Ca, respectively. Both proxies are somewhat sensitive to carbonate ion concentration. In addition, a detailed mechanistic understanding does not exist for many temperature proxies (e.g., UK'37, TEX86, Mg/Ca). All of these factors contribute to uncertainties in the interpretation of past conditions, particularly for extinct taxa, for which one cannot establish robust empirical calibrations of the proxy. A technique that may not be subject to these limitations is the new carbonate 'clumped isotope' thermometer. Clumped isotope thermometry is based on the principle that ordering, or 'clumping', of heavy isotopes into bonds with or near each other in molecules, minerals or organic moieties is a temperature dependent phenomenon. In carbonates, rare heavy isotopes (13C, 18O) occur in a pool of abundant light isotopes. The proportion of 13C and 18O that are bound to each other within the carbonate mineral lattice is predicted to be temperature dependent based on principles of statistical thermodynamics. In practice, the carbonate clumped isotope thermometer is based on analyses of 13C18O16O in CO2 produced by acid digestion of carbonates. With this fellowship, I propose to develop the first calibration of the carbonate 'clumped isotope' thermometer in planktic and benthic foraminifera, and coccoliths. To date, a limited number of measurements have been made to calibrate ?47 in inorganic calcite precipitated at known temperatures (4 samples), in fish otoliths (8 samples), mollusks (3 samples), brachiopods (3 samples), and coral (3 samples). There has not yet been a validation of the clumped isotope thermometer from cultured biogenic samples, detailed field-based sampling, and no measurements have been made of foraminifera and coccoliths - all of which are requisite for paleoceanographic studies. In addition to calibrating this new isotopic thermometer in cultured and coretop foraminifera and coccoliths, I will use these data to test models for the origin of 'vital effects' in 18O and 13C. I will also apply this this thermometer to Last Glacial Maximum samples from the warm pool in the western tropical Pacific Ocean. The West Pacific warm pool is the warmest open ocean region and a benchmark for climate models. Reconstructions of the glacial-interglacial change in sea surface temperatures in the region vary from 1 to 6°C, differing systematically between methods. Finally, I will apply this thermometer to Paleocene-Eocene boundary samples from the Southern Ocean, in order to constrain the warming associated with the massive release of carbon.