A dual clumped isotope approach to characterize disequilibrium in terrestrial carbonates

碳酸盐矿物(如方解石、碳酸钙)在其化学和同位素组成中记录了有关环境的信息，是地球气候系统、海洋和大气化学以及生物如何随时间演变的主要档案。与海洋生态系统相比，大陆环境承受着更大的气候变化负面后果，如火灾、干旱和洪水，因此，我们必须了解如何正确地将陆地沉积物中的化学信号与气候和环境参数(如温度、缺水)相对应。在陆地环境中形成的碳酸盐往往在矿物和水之间达到平衡之前迅速沉淀，扭曲了矿物记录的化学成分。这项研究将通过对美国西部和加拿大西部湖泊和湿地中形成的现代碳酸盐和化石碳酸盐的调查，研究快速矿物形成过程中的不平衡对重要气候档案的作用。了解地球表面环境和水资源如何应对不同的气候状态，特别是全球暖期，对于制定可行的战略以减轻对人类人口的影响至关重要。这项研究将为基于稳定同位素的陆地地表水可获得性和温度记录提供新的背景。研究小组还将在宾夕法尼亚州农村高中开发面对面和虚拟的气候科学课程和STEM职业规划，并将虚拟教育模块发布到供K-12教育人员开放访问的存储库。要了解陆地生态系统对全球或区域水文气候扰动和高温事件的响应，我们必须了解陆地沉积物如何将古环境信息存档。由于温度、水平衡和矿物饱和状态的自然波动，碳酸盐矿物经常在湖泊、湿地和土壤中快速沉淀--可能在达到同位素平衡之前。将这些矿物的同位素组成解释为热力学平衡的记录可能会导致温度和水气候重建的重大误差。这项研究将描述现代(加拿大卡里布高原)、更新世(加利福尼亚州莫诺湖)和古近纪(科罗拉多州绿河FM、怀俄明州/犹他州)湖泊和湿地中由不同机制形成的一套碳酸钙相中的不平衡双束同位素信号(∆47-∆48)，以产生更可靠的同位素格架来解释成岩作用不同阶段地质记录中的陆地碳酸盐。沉积学将与同位素分析相结合，以识别特定陆相碳酸盐生产模式的∆47-∆48“不平衡信号”--热力学平衡的幅度和趋势。研究人员预测，快速形成的陆相碳酸盐相将记录到∆47和∆48的不平衡，而形成较慢的相将记录到平衡，这是由于每个矿物形成微环境中的碳循环机制所致的相特定依赖。这一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智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

Carbonate minerals (e.g. calcite, calcium carbonate) record information about the environment in their chemical and isotopic compositions, and are a primary archive of how Earth’s climate system, ocean and atmospheric chemistry, and biology have evolved through time. Continental environments experience greater negative consequences of climate change, such as fire, drought, and floods, than marine ecosystems, and thus it is critical that we understand how to correctly map chemical signals in terrestrial sediments to climatic and environmental parameters (e.g. temperature, water scarcity). Carbonates that form in terrestrial environments often precipitate rapidly before equilibrium is achieved between the mineral and water, skewing the chemistry recorded by the mineral. This research will investigate the role of disequilibrium imparted during rapid mineral formation on important climate archives through an investigation of modern and fossil carbonates formed in lakes and wetlands in the western US and Canada. Understanding how Earth’s surface environments and water resources have responded to varied climate states, and in particular, globally warm periods, is crucial in developing viable strategies to mitigate the effects on human populations. This study will provide new context to stable isotope-based records of land surface water availability and temperatures. The research team will also develop in-person and virtual climate science curriculum and STEM career programming in rural Pennsylvania high schools, and publish virtual education modules to an open-access repository for K-12 educators.To understand the response of terrestrial ecosystems to global or regional hydroclimate perturbations and hyperthermal events, we must understand how terrestrial sediments archive paleoenvironmental information. Carbonate minerals often precipitate rapidly—potentially before isotopic equilibrium is achieved—within lakes, wetlands, and soils due to natural fluctuations in temperature, water balance, and mineral saturation state. Interpreting the isotopic compositions of these minerals as a record of thermodynamic equilibrium can lead to significant error in temperature and hydroclimate reconstructions. This study will characterize disequilibrium dual clumped isotope signals (∆47-∆48) in a suite of calcium carbonate facies that form by different mechanisms in modern (Cariboo Plateau, Canada), Pleistocene (Mono Lake, California), and Paleogene (Green River Fm, Colorado/Wyoming/Utah) lakes and wetlands to generate a more robust isotopic framework for interpreting terrestrial carbonates in the geologic record at different stages of diagenesis. Sedimentology will be partnered with isotope analyses to discern the ∆47-∆48 “disequilibrium signal”—the magnitude and trend from thermodynamic equilibrium—for specific modes of terrestrial carbonate production. The researchers predict that terrestrial carbonate facies that form rapidly will record ∆47 and ∆48 disequilibrium whereas facies that form more slowly will record equilibrium, with the facies-specific dependence due to the carbon cycling mechanisms within each mineral formation micro-environment.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.