Collaborative Research: Late Pleistocene paleoclimatology from soil carbonate pendants in the Colorado Plateau.

本研究将检查保存在科罗拉多高原Capitol Reef- Boulder山区土壤中成土碳酸盐涂层层状沉积物中的同位素和地球化学记录。首先，该团队将通过显微镜、高分辨率x射线测绘和Th/U年龄测定来检查涂层层状中地层秩序的保存情况。将对保存完整地层的涂层进行微采样，以进行详细的Th/U年龄样条，稳定同位素分析和微量元素分析。研究小组将比较从土壤-空气界面以下不同深度收集的涂层中稳定同位素变化的准确年代剖面，以重建在测量时间间隔内发生的生态和气候变化的时间和幅度。本研究将评估悬垂记录中的不连续性问题，这可能与轨道时间尺度上的气候变化有关。碳酸盐形成的时间和机制将通过原位土壤湿度、呼吸和温度测量来评估。现代和化石成土碳酸盐岩的稳定同位素分析促进了对大陆古气候学的认识，并记录了世界范围内的生态变化。大多数成土碳酸盐的稳定同位素研究都是在相当粗的分辨率下取样土壤碳酸盐；只有少数人研究了土壤层位内大碎屑的土壤碳酸盐包覆层的稳定同位素记录。这项工作将测试厚的、层状良好的、成壤的碳酸盐涂层，以记录有意义的古气候信号，根据它们的稳定同位素记录（13C/12C和18O/16O），当涂层保存完整的地层。如果这是真的，并且有一些初步的Th/U和稳定同位素数据支持这一点，那么世界上的沙漠可能包含了大量未开发的过去大陆气候和生态变化的定量档案。这个项目是犹他大学和西部州立科罗拉多大学的合作成果。它将增加研究机构和本科院校的教育机会，其成果将纳入犹他大学每年教授的一门国际课程，在人类学、生态学、法医学、地质学、水文学、海洋学和动物学中使用稳定同位素作为示踪剂。

This study will examine isotopic and geochemical records preserved in the laminae of pedogenic carbonate coatings in soils in the Capitol Reef--Boulder Mountain region of the Colorado Plateau. First, the team will check for preservation of stratigraphic order in the laminae of coatings by microscopy, high-resolution X-ray mapping, and Th/U age dating. Coatings that preserve an intact stratigraphy will be micro-sampled for detailed Th/U age transects, stable isotope analysis, and trace element analysis. The team will compare well-dated profiles of stable isotope shifts from coatings collected at various depths below the soil-air interface to reconstruct the timing and magnitude of ecological and climatological changes that occurred over the measured time interval. This study will evaluate the problem of discontinuities in the pendant record which could be related to climate change on orbital time scales. Timing and mechanisms of carbonate formation will be evaluated with in situ soil moisture, respiration, and temperature measurements. Stable isotope analysis of modern and fossil pedogenic carbonate has advanced the understanding of continental paleoclimatology, as well as documenting worldwide ecological shifts. Most stable isotope studies of pedogenic carbonate have sampled soil carbonate at a fairly coarse resolution; only a few have studied the stable isotope record of soil carbonate coatings of the large clasts within a soil horizon. This work will test thick, well-laminated, pedogenic carbonate coatings for records of a meaningful paleoclimate signal in terms of their stable isotope record (13C/12C and 18O/16O) when coatings preserve an intact stratigraphy. If true, and there is some preliminary Th/U and stable isotope data that supports this, then the world's deserts may contain a vast and untapped quantitative archive of past continental climactic and ecological variability. This project is a collaborative effort between the University of Utah and Western State Colorado University. It will enhance education opportunities for both a research institution and an undergraduate institution, and its results will be incorporated into an international course, taught each year at the University of Utah, using stable isotopes as tracers in anthropology, ecology, forensics, geology, hydrology, oceanography, and zoology.