Accomplishment-Based Renewal: Testing Hypothesized CO2 Forcing of Climate, Glaciation, and Biotic Change During the End Carboniferous

ABR：在石炭纪末期测试假设的CO2强迫气候，冰川和生物变化。通过与同事和学生的合作，ABR项目的重点是关于晚古生代冰期的几个关键问题，这些问题仍然没有得到很好的约束。例如，二氧化碳变化的真实幅度，晚古生代气候敏感性，以及与区域水文气候、土壤生产力、冰盖稳定性和古热带植被主要重构之间联系的性质。提出的双组分研究计划集中在石炭世末~ 9myr区间，特别是假设的？气候事件吗?在宾州中后期的过渡时期组分1将评估古二氧化碳分压在这一区间的变化，及其在大范围干旱和主要植被重建中的作用。预期的产品包括一个周期尺度（~105年）的基于气孔指数的古二氧化碳分压记录，该记录使用了来自伊利诺斯盆地的两个长期且已被充分了解的湿地种子蕨类类群。从选定的环区收集的旱生瓦尔喀斯针叶树角质层将允许比较基于si的湿地和旱地植物区系的二氧化碳估计值以及间冰期-冰川尺度的二氧化碳变异性。对同一化石皮的化合物特异性同位素分析（äD和ä13C）将进一步限制伊利诺斯盆地古干旱的发生速率和程度，并检验二氧化碳分压、陆地古热带干旱和植物生态重构之间的因果关系。在可控的大气O2:CO2比例和推断的石炭纪气候条件下，一项为期4年的长期植物生长实验将为基于化石的趋势提供新的见解。将结果与古植物学数据和我们的古气候代理记录相结合，将用于为我们的气候建模工作开发适当的植被反馈组件。第二个研究部分将利用已收集的两个古热带盆地的牙形刺（CAI 1-3）在同一末石炭世段建立旋回尺度ä18O磷灰石记录。目的是验证这样一种假设，即二氧化碳强迫的全球变暖时期也推动了冰盖消融和高频（104-105年）冰川流动幅度的减小。通过合作，我们将测试？碳酸盐块状同位素？从同一地质剖面的一套保存异常完好且经过成岩筛选的腕足动物中确定降水的海面温度的方法。我们预计，对于保存最好的腕足动物，这种方法应该可以重建宾夕法尼亚州的SSTs和ä18Oseawater，并最终对LPIA期间冰体积的相对变化进行迄今为止最严格的评估。

ABR: Testing Hypothesized CO2 Forcing of Climate, Glaciation & Biotic Change During the End-CarboniferousIsabel MontanezEAR-1024737ABSTRACTThe focus of this ABR project, through collaboration with colleagues and students, is several key issues regarding the late Paleozoic Ice Age that remain poorly constrained ? i.e., the true magnitude of CO2 shifts, late Paleozoic climate sensitivity, and the nature of the linkages to regional hydroclimate, soil productivity, ice sheet stability, and major restructuring of paleotropical vegetation. The proposed two-component research plan focuses on a ~9 Myr interval of the end-Carboniferous, in particular a hypothesized ?climate event? during the mid-to-late Pennsylvanian transition. Component 1 will evaluate how paleo-pCO2 varied through this interval, and its role in widespread aridity and major vegetation restructuring. Anticipated products include a cyclothem-scale (~105 yr) stomatal index-based record of paleo-pCO2 using two long-ranging and well understood, wetland seed-fern taxa from the Illinois Basin. Integration of xerphytic walchian conifer cuticles from select cyclothems will permit comparison of SI-based CO2 estimates for wet- and dry-land flora and interglacial-glacial-scale CO2 variability. Compound-specific isotopic analysis (äD and ä13C) of the same fossil cuticles will further constrain the rate of onset and magnitude of paleoaridity in the Illinois Basin and test for causality between pCO2, terrestrial paleotropical aridity, and floral ecological restructuring. A proposed 4-year long-duration, plant growth experiment under controlled atmospheric O2:CO2 ratios and inferred Carboniferous climate conditions will provide novel insight into the fossil-based trends. Integration of results with paleobotanical data and our paleoclimate proxy records will be used to develop an appropriate vegetation-feedback component for our climate modeling efforts. The 2nd research component will develop a cyclothem-scale ä18O apatite record using already collected conodonts (CAI 1-3) from two paleotropical basins for the same end-Carboniferous interval. The objective is to test the hypothesis that periods of CO2-forced global warming also drove ice sheet ablation and a reduction in the amplitude of high-frequency (104-105 yr) glacioeustasy. Through collaboration, we will test the potential of the ?carbonate clumped isotope? method to define sea-surface temperatures of precipitation from a suite of exceptionally well-preserved and diagenetically screened brachiopods from the same geological sections. We anticipate that for the best-preserved brachiopods, this approach should permit reconstruction of Pennsylvanian SSTs and ä18Oseawater, and ultimately the most rigorous evaluation of relative changes in ice volume during the LPIA to date.