EAR-PF: Seeing through carbonate diagenesis using the triple oxygen isotope system

EAR-PF：使用三氧同位素系统透视碳酸盐岩成岩作用

• 批准号: 1952615
• 负责人: Jordan Wostbrock
• 金额: $ 17.4万
• 依托单位: Wostbrock, Jordan
• 依托单位国家: 美国
• 项目类别: Fellowship Award
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-02-01 至 2023-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1952615&HistoricalAwards=false
• 关键词: EAR; PF; Seeing; through; carbonate

An NSF EAR Postdoctoral Fellowship has been granted to Dr. Jordan Wostbrock to carry out research and educational activities at Yale University under the mentorship of Dr. Noah J. Planavsky. This project investigates how well carbonate rocks preserve the initial environmental conditions under which the rock formed. Carbonates that form in marine settings are commonly used to reconstruct past ocean temperatures to see how oceans change between glacial and interglacial cycles (greenhouse/icehouse climates). The ratios of oxygen isotopes in carbonate rocks are used to calculate the temperature in which these rocks formed. However, using traditional measurements of the oxygen isotope ratios (i.e. using only the Oxygen-18/Oxygen-16 ratio) makes it difficult to figure out if the oxygen isotope ratios measured in the rock are from the initial deposition or if the oxygen isotope ratios have changed after deposition. A novel oxygen isotope measurement technique that looks at an additional oxygen isotope ratio (the Oxygen-17/Oxygen-16 ratio) will be used to better constrain the depositional environments of marine carbonate rocks. This additional variable will enable marine scientists to better determine the conditions of ancient marine environments using the rock record. For example, biologists and paleontologists might be able to use this tool to look at micro-environmental changes that affect coral survivability or that might have impacted evolution. As a female in a STEM field, Dr. Jordan Wostbrock will actively seek female engagement in STEM by recruiting an undergraduate woman as an assistant in the laboratory, mentor undergraduate research experiences, and serve as a mentor for the Women in Science at Yale program. This project will use the triple oxygen isotope composition (combined 17O/16O and 18O/16O measurements) of carbonates to examine how oxygen isotope values change during alteration. It will be the first in-depth application of the triple oxygen isotope system of carbonates in a marine setting and will focus on two main tasks: 1) Measure the triple oxygen isotope compositions of a known diagenetic environment of the Bahama Platform to create a triple oxygen isotope equipped reaction transport model and 2) Measure the triple oxygen isotope compositions of Archean through Cretaceous carbonate rocks to explore whether the observed increase in oxygen isotope values is related to changing ocean isotopic composition, temperature, or preservation quality. Dr. Wostbrock will combine other geochemical systems such as Sr and Ca as well as hydrologic conditions to predict how carbonate oxygen isotope composition changes in the shallow marine environment. A better understanding of diagenesis in shallow marine settings will change our understanding of how the rock record preserves ocean geochemistry. Better understanding of ocean dynamics will assist in the prediction of how oceans respond to external forces during a changing climate. This study will try to address the 50-year-old question as to whether the secular change seen in the carbonate record is a preservation issue, a change in oxygen isotope composition of the ocean, or a change in ocean temperature.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

Jordan Wostbrock博士获得美国国家科学基金会EAR博士后奖学金，在Noah J. Planavsky博士的指导下在耶鲁大学开展研究和教育活动。这个项目研究碳酸盐岩如何很好地保存岩石形成的初始环境条件。在海洋环境中形成的碳酸盐通常被用来重建过去的海洋温度，以观察海洋在冰期和间冰期循环（温室/冰窖气候）之间的变化。碳酸盐岩中氧同位素的比值被用来计算这些岩石形成时的温度。然而，使用传统的氧同位素比值测量方法（即仅使用氧-18/氧-16比值）很难确定岩石中测量的氧同位素比值是来自初始沉积还是沉积后氧同位素比值发生了变化。一种新的氧同位素测量技术，通过观察额外的氧同位素比值（氧-17/氧-16比值），将用于更好地约束海相碳酸盐岩的沉积环境。这个额外的变量将使海洋科学家能够利用岩石记录更好地确定古代海洋环境的条件。例如，生物学家和古生物学家可能能够使用这个工具来观察影响珊瑚生存能力或可能影响进化的微环境变化。作为一名STEM领域的女性，Jordan Wostbrock博士将积极寻求女性参与STEM，招募一名本科女性作为实验室助理，指导本科生的研究经验，并担任耶鲁大学女性科学项目的导师。本项目将利用碳酸盐的三重氧同位素组成（17O/16O和18O/16O组合测量）来研究氧同位素值在蚀变过程中的变化。这将是首次在海洋环境中深入应用碳酸盐三氧同位素系统，并将侧重于两个主要任务：1)测量Bahama平台已知成岩环境的三氧同位素组成，建立三氧同位素装备的反应输运模型；2)测量太古宙至白垩纪碳酸盐岩的三氧同位素组成，探讨氧同位素值的升高是否与海洋同位素组成、温度或保存质量的变化有关。Wostbrock博士将结合其他地球化学系统，如Sr和Ca，以及水文条件来预测浅海环境中碳酸盐氧同位素组成的变化。更好地了解浅海环境中的成岩作用将改变我们对岩石记录如何保存海洋地球化学的理解。更好地了解海洋动力学将有助于预测海洋在气候变化期间如何对外力作出反应。这项研究将试图解决一个50年来的问题，即在碳酸盐记录中看到的长期变化是保存问题，是海洋氧同位素组成的变化，还是海洋温度的变化。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。