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

9814637 steiner在二叠纪期间，伴随泛古大陆季风环流演化的高分辨率气候变化的详细记录很少。此外，盘古大陆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，这可能是由二叠纪大气中二氧化碳分压水平的增加引起的。古土壤是古环境和古气候信息的敏感来源，它提供了古水文、降水水平和季节性的多种代用物，这些代用物共同反映了区域古气候条件。此外，同一古土壤中的成土碳酸盐可以提供古co2和相关全球温度变化的直接记录，而不依赖于其他古土壤代用物提供的记录。我们的合作研究团队计划通过对德克萨斯州和俄克拉何马州陆相序列的二叠纪古土壤进行沉积学、岩石学、地球化学、磁地层和地质年代学综合分析，确定赤道泛大陆西部第一个详细的古气候重建和古pco2记录。本研究有三个主要目标：(1)开展全面的野外和实验室古土壤研究，以确定最准确记录区域气候时间变化的沉积学、矿物学、地球化学和生物代用物。(2)通过对成土碳酸盐和相关脊椎动物牙釉质进行稳定同位素分析，以及对同一古土壤陆相有机质进行化合物特异性稳定同位素分析，重建整个二叠纪时期大气pCO2的演化。(3)通过将以下技术应用于德克萨斯州和俄克拉何马州陆地序列，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)火山烟碱、成土铁硫酸盐（钠黄钾铁矾）和蒸发矿物（朗白铁矿）的40Ar/39Ar定年，b)成土碳酸盐的U-Pb定年，c)蒸发岩中包裹的富镁自生粘土的Rb-Sr定年，d)晚二叠世陆相演替的详细磁地层研究。由此产生的古气候和古pCO2记录应该(1)对超大季风发展和相关气候系统演化提供显著增强的时间约束；(2)有助于约束大气pCO2水平升高可能导致的冰川消融的时间；(3)为测试和约束数值模式结果提供详细和校准的古气候/古pCO2记录。(4)极大地促进了我们的陆地记录与来自其他陆地沉积物的气候记录以及海洋古气候记录的相关性；(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“奠定了基础”。

9814637SteinerFew 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.