Collaborative Research: Interpreting clumped isotope temperatures and δ18O records from pedogenic carbonate: influence of climate, seasonality, and elevation

一种常见地质材料碳酸钙的新同位素测量技术，有可能揭示大陆温度和环境条件在整个地球历史中的变化。这项技术被称为聚集同位素测温法，利用碳酸钙中碳和氧的重同位素随温度变化的分组。含碳酸钙土壤在陆地地质记录中相对常见，并为重建过去的地球表面环境提供了有吸引力的目标。然而，虽然聚集同位素测温的理论基础是强大的，确切地说，环境条件是如何反映在土壤碳酸盐形成温度还没有很好的理解。因此，开发一个框架来理解影响碳酸盐形成时间的环境因素，是解锁过去地表温度的潜在丰富记录和增强对地球认识的关键。的古气候。来自锡拉丘兹大学和华盛顿大学的一组研究人员与智利天主教大学和阿根廷Nivología，Glaciología y Ciencias Ambientales研究所（IANIGLA）的研究人员合作，将在南纬30°附近的安第斯山脉及其附近进行为期两年的研究，以确定碳酸盐聚集同位素温度计如何记录现代到100的温度，千年前的土壤，重点是如何将这些方法应用于了解地球过去在大陆上的表面状况。主要研究目标是量化：1）季节性降水、气温和植被对土壤碳酸盐形成时间和温度的影响; 2）全新世的聚集同位素温度（11，500年）土壤碳酸盐和计算的土壤水氧同位素值预测了现代海拔和降水的同位素组成;以及3）通过探索凝块同位素温度如何随土壤碳酸盐年龄和发育阶段而变化来研究长时间（1000至10，000年）尺度上信号整合的影响。安第斯实地是这项研究的理想地点，因为该地区4公里的地形起伏提供了广泛的年平均温度和季节温度。安第斯山脉的东西两侧也有相反的雨季和植被类型和密度的梯度，使这项研究梳理除了这些因素对土壤碳酸盐的聚集同位素温度的影响。这项研究将支持两名地球科学博士生的教育和培训，并促进两所美国大学及其南美同行之间的合作。这项研究的组成部分将用于大学和高中教学，通过参与的专业人员在各自的国家高中教师的专业发展计划。这项研究的结果将在科学期刊，专业会议，PI网站，大学课程以及UW外展计划Rockin' Out的实践活动中传播。该项目将通过开发一种可在许多地方应用于古气候和古测高研究的工具，使更广泛的科学界受益，并可能改变研究人员解释古土壤稳定同位素数据的方式。

A new isotopic measurement technique of a common geologic material, calcium carbonate, has the potential to reveal how continental temperatures and environmental conditions have changed throughout Earth history. The technique, called clumped isotope thermometry, exploits the temperature-dependent grouping of the heavy isotopes of carbon and oxygen in calcium carbonate. Calcium carbonate bearing soils are relatively common in the terrestrial geologic record and present attractive targets for reconstructing past earth surface environments. However, while the theoretical basis for clumped isotope thermometry is robust, exactly how environmental conditions are reflected in soil carbonate formation temperatures is not well understood. Thus, developing a framework for understanding the environmental factors that influence the timing of carbonate formation is the key to unlocking a potentially rich record of past surface temperatures and enhancing the understanding of Earth?s terrestrial paleoclimates. A team of researchers from Syracuse University and the University of Washington, in collaboration with researchers from the Pontificia Universidad Cátolica de Chile, and the Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales (IANIGLA) in Argentina will conduct a two-year study in and adjacent to the Andes near 30°S latitude to determine how the carbonate clumped isotope thermometer records temperatures in modern to 100,000 year old soils, with a focus on how these methods can be applied to understand Earth's past surface conditions on the continents. The primary research goals are to quantify: 1) the influence of seasonal precipitation, air temperature, and vegetation on the timing and temperature of soil carbonate formation; 2) how well clumped isotope temperatures of Holocene (11,500 year old) soil carbonates and calculated soil water oxygen isotopic values predict modern elevation and the isotopic composition of precipitation; and 3) the impact of signal integration over long (1000 to 10,000 year) timescales by exploring how clumped-isotope temperature varies with soil carbonate age and development stage. The Andean field site is ideal for this study because the 4 km of topographic relief in this area provides a wide range of mean annual and seasonal temperatures. The east and west sides of the Andes also have opposing rainy seasons and gradients in vegetation type and density, enabling this study to tease apart the influence of these factors on clumped isotope temperatures of soil carbonate. This study will support the education and training of two doctoral students in the Earth Sciences as well as foster collaboration among two US universities and their South American counterparts. Components of this research will be used in University and high school teaching via the participation of the PIs in professional development programs for high school teachers in their respective states. The results of this study will be disseminated in scientific journals, professional conferences, the PIs' websites, university courses, and a hands-on activity for the UW's outreach program, Rockin' Out. The project will benefit the broader scientific community by developing a tool that can be applied in many places for paleoclimate and paleoaltimetry research, and potentially change the way researchers interpret stable isotope data for paleosols.