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

对一种常见的地质物质碳酸钙的一种新的同位素测量技术，有可能揭示整个地球历史上大陆的温度和环境条件是如何变化的。这项技术被称为团块同位素测温法，它利用了碳酸钙中碳和氧的重同位素的温度依赖性分组。含碳酸钙土壤在陆地地质记录中相对常见，是重建过去地球表面环境的有吸引力的目标。然而，虽然团块同位素测温的理论基础是坚实的，但环境条件究竟如何反映在土壤碳酸盐地层温度中还不是很清楚。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表面温度的潜在丰富记录和增强对地球的理解的关键。S陆生古气候。来自锡拉丘兹大学和华盛顿大学的一组研究人员，与智利教皇大学Cátolica和阿根廷环境科学研究所（IANIGLA）的研究人员合作，将在南纬度30°附近的安第斯山脉及其附近进行为期两年的研究，以确定碳酸盐团块同位素温度计如何记录现代到10万年前土壤的温度。重点是如何应用这些方法来了解地球大陆过去的表面状况。主要研究目标为：1)季节降水、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（11500年前）土壤碳酸盐的团块同位素温度和计算的土壤水氧同位素值如何预测现代海拔和降水的同位素组成；3)通过探索块状同位素温度随土壤碳酸盐年龄和发育阶段的变化，在1000 ~ 10000年的时间尺度上对信号积分的影响。安第斯野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梯度，使本研究能够梳理出这些因素对土壤碳酸盐块状同位素温度的影响。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。本研究的组成部分将通过pi参与各自州的高中教师专业发展计划，在大学和高中教学中使用。这项研究的结果将在科学期刊、专业会议、pi网站、大学课程和华盛顿大学外展项目rock ' Out的实践活动中传播。该项目将通过开发一种可以在许多地方应用于古气候和古高度计研究的工具，并有可能改变研究人员解释古土壤稳定同位素数据的方式，从而使更广泛的科学界受益。

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.