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

ABR：测试石炭纪末期气候、冰川和生物变化的假设二氧化碳压力Isabel MontanezEAR-1024737 ABR项目的重点是，通过与同事和学生的合作，关于晚古生代冰河时代的几个关键问题仍然缺乏约束？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重大重组的联系的性质。拟议的双组分研究计划集中在石炭纪末期的~9Myr间隔，特别是假想的气候事件？在宾夕法尼亚中晚期的过渡时期。组成部分1将评估古二氧化碳在这段时间内如何变化，以及它在大范围干旱和主要植被重建中的作用。预期的产品包括基于旋回尺度(约105年)气孔指数的古二氧化碳记录，该记录使用了来自伊利诺伊盆地的两个长期的、众所周知的湿地种子蕨类。来自特定植被的旱生针叶针叶角质层的整合将使基于SI的湿地和旱地植物二氧化碳估算值与间冰期-冰川尺度二氧化碳变异性的比较成为可能。对同一化石角质层的化合物特定同位素分析(äD和ä13C)将进一步限制伊利诺伊盆地古干旱的开始速度和程度，并测试二氧化碳、陆地古热带干旱和植物生态重建之间的因果关系。一项拟议的为期4年的长时间植物生长实验，在受控的大气O2：CO2比率和推断的石炭纪气候条件下，将为化石趋势提供新的见解。结果与古植物学数据和我们的古气候替代记录的整合将被用来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从两个古热带盆地采集的同一石炭纪末的牙形刺(CaI1-3)，开发旋回尺度的18O磷灰石记录。其目的是验证这样一种假设，即二氧化碳迫使全球变暖的时期也推动了冰盖的消融和高频(104-105年)冰川稳定幅度的降低。通过合作，我们将测试碳酸盐块状同位素的潜力。方法从同一地质剖面中一套保存特别完好、经过成岩筛选的腕足类确定降水的海面温度。我们预计，对于保存最完好的腕足类，这种方法应该能够重建宾夕法尼亚SST和ä18O海水，并最终对LPIA期间冰量的相对变化进行最严格的评估。

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.