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，气候变化对大陆环境的负面影响更大，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映射到气候和环境参数（如温度、缺水）。在陆地环境中形成的碳酸盐通常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性质。本研究将通过对美国西部和加拿大湖泊和湿地中形成的现代和化石碳酸盐的调查，探讨在快速矿物形成过程中所传递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，特别是全球变暖时期，对于制定减轻对人口影响的可行策略至关重要。这项研究将为陆地地表水可用性和温度的稳定同位素记录提供新的背景。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K-12教育工作者的开放访问存储库中。为了了解陆地生态系统对全球或区域水文气候扰动和过热事件的响应，我们必须了解陆地沉积物如何存档古环境信息。碳酸盐矿物通常在湖泊、湿地和土壤中由于温度、水平衡和矿物饱和状态的自然波动而迅速沉淀——可能在同位素平衡达到之前。将这些矿物的同位素组成解释为热力学平衡的记录可能导致温度和水文气候重建的重大误差。本研究将对现代（加拿大Cariboo高原）、更新世（加利福尼亚州Mono湖）和古近系（科罗拉多州/怀俄明州/犹他州格林河Fm）湖泊和湿地中以不同机制形成的一套碳酸钙相中的不平衡双团块同位素信号（∆47-∆48）进行表征，以生成一个更可靠的同位素框架，用于解释地质记录中不同成岩阶段的陆相碳酸盐。沉积学将与同位素分析相结合，以辨别出陆地碳酸盐生产的特定模式的∆47-∆48“不平衡信号”——来自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∆47和∆48不平衡，而形成较慢的陆相碳酸盐相将记录平衡，并且由于每种矿物形成微环境中的碳循环机制而具有相特异性依赖。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。

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.