COLLABORATIVE RESEARCH: Integrated Analysis of Permian Terrestrial Sediments & Paleosols: Defining a High-Resolution Proxy for the Evolution of Western Equatorial Pangean Clima

关于二叠纪期间可能伴随着盘古季风环流演变的气候制度的高分辨率变化的详细记录仍然存在。此外，盘古气候的地质气候指标和数值模型表明，巨型季风的发展伴随着全球变暖的加剧，这可能是由于二叠纪大气中二氧化碳水平的增加所致。古土壤是古环境和古气候信息的敏感来源，它提供了多个共同反映区域古气候条件的古水文学、降水量和季节性指标。此外，同一古土壤中的成壤碳酸盐可以提供与其他古土壤替代物提供的记录无关的古二氧化碳及其相关全球温度变化的直接记录。我们的合作研究小组建议通过对德克萨斯州和俄克拉何马州陆地序列中的二叠纪古土壤进行综合的沉积学、岩石学、地球化学、磁性地层学和年代学分析，来确定赤道西部盘古地区第一个详细的古气候重建和古二氧化碳记录。这项研究以三个主要目标为指导：(1)开展全面的古土壤野外和实验室研究，以确定最准确地记录区域气候时间变化的沉积学、矿物学、地球化学学和生物学替代物。(2)通过对成壤碳酸盐及其伴生脊椎动物牙釉质进行稳定同位素分析，以及对同一古土壤中的陆地有机质进行化合物特异性稳定同位素分析，重建大气PCO2在二叠纪的演化。(3)通过将下列技术应用于德克萨斯州和俄克拉何马州的陆相序列，建立一个显著改进的时间框架，用于校准详细的古气候和古PCO2记录：a)火山砂岩、成壤硫铁酸盐(钠黄钾镁铁矿)和蒸散矿物(朗贝石)的40Ar/39Ar测年，b)成土碳酸盐的U-Pb测年，c)蒸发岩中富镁自生粘土的Rb-Sr测年，以及d)晚二叠世陆相序列的详细磁性地层研究。由此产生的古气候和古pCO2记录应(1)对气候系统的短期发展和相关演化提供显著的时间约束。(2)有助于限制大气二氧化碳水平增加可能导致的冰川消融的时间，(3)提供详细和校准的古气候/古二氧化碳记录，用于测试和约束数值模型结果，(4)极大地促进我们的陆地记录与来自其他陆地沉积的气候记录以及海洋古气候记录的关联，以及(5)为更好地理解可能导致二叠纪末大规模灭绝的古环境压力奠定基础。

9814639RasburyFew detailed records of the high-resolution variations in climate regimes that likely accompanied the evolution of Pangean monsoonal circulation during the Permian exist. Moreover, geologic climate indicators and numeric models for Pangea suggest that megamonsoon development was accompanied by increased global warming possibly brought on by increased pCO2 levels in Permian atmospheres. Paleosols are a sensitive source of paleoenvironmental and paleoclimate information by offering multiple proxies of paleohydrology, precipitation levels, and seasonality that collectively reflect regional paleoclimatic conditions. In addition, pedogenic carbonates in the same paleosols can provide a direct record of paleo-pCO2 and associated changes in global temperature that is independent from the record provided by other paleosol proxies. Our collaborative research team proposes to define the first detailed paleoclimate reconstruction and paleo-pCO2 record for western equatorial Pangea by carrying out an integrated sedimentologic, petrologic, geochemical, magnetostratigraphic, and geochronologic analysis of Permian paleosols in the terrestrial successions of Texas and Oklahoma.This research is directed by three main objectives: (1) to carry out a comprehensive field and laboratory study of paleosols in order to identify those sedimentologic, mineralogic, geochemical, and biologic proxies that most accurately record temporal changes in regional climate. (2) To reconstruct the evolution of atmospheric pCO2 throughout Permian time by carrying out a stable isotope analysis of pedogenic carbonates and associated vertebrate tooth enamel, as well as compound-specific stable isotope analysis of terrestrial organic matter from the same paleosols. (3) To develop a significantly improved temporal framework for calibration of the detailed paleoclimate and paleo-pCO2 records by applying the following techniques to the Texas and Oklahoma terrestrial successions: a) 40Ar/39Ar dating of volcanic sanidines, pedogenic Fe-sulfates (natrojarosite), and evaporitic minerals (langbeinite), b) U-Pb dating of pedogenic carbonates, c) Rb-Sr dating of Mg-rich authigenic clays encapsulated within evaporites, and d) detailed magnetostratigraphic study of the Late Permian terrestrial successions.The resulting paleoclimate and paleo-pCO2 records should (1) provide significantly enhanced temporal constraints on megamonsoon development and associated evolution of the climate system, (2) contribute toward constraining the timing of deglaciation that would have been brought on by increased atmospheric pCO2 levels, (3) provide detailed and calibrated paleoclimate/paleo-pCO2 records for testing and constraining numeric model results, (4) greatly facilitate the correlation of our terrestrial records to climate records derived from other terrestrial deposits as well as to marine paleoclimate records, and (5) 'set the stage' for better understanding the paleoenvironmental stresses that may have contributed to the massive end-Permian extinction.