Changes in Paleosol Morphology and Geochemistry Associated with Mid-Paleozoic Afforestation and Decline in Atmospheric pCO2

9418183莫拉拟议的研究调查在硅罗-泥盆纪时期保存下来的古土壤和土壤成因碳酸盐形态和地球化学的变化，这是陆地生态系统快速演化和多样化的时期。陆地植物的进化导致植物体型越来越健壮，生根能力越来越强，陆地表面的植树造林也越来越普遍。陆地维管植物的发育和日益丰富可能有助于提高风化速率，并将大气二氧化碳从中古生代的很高水平降低到石炭-二叠纪的近现代水平。这项拟议的研究将对植树造林、增加风化剖面以及促进土壤碳酸盐稳定同位素组成变化的假说进行评估。这项拟议的研究将重点对美国和加拿大阿巴拉契亚海域露头暴露的10个地层单位(主要是红层)的志罗-泥盆纪古土壤进行形态和地球化学分析。详细的古土壤宏观和微观形态特征、古土壤厚度的估算、土壤主要元素和微量元素的质量平衡评价以及成壤碳酸盐相的稳定同位素分析将与这些单元现有的古生物信息相结合，以表征维管植物在陆地表面植树造林的“土壤学特征”。这一结果将允许使用Cerling的土壤碳酸盐古生物量计对这一深刻变化期间的大气二氧化碳进行详细评估。这些结果将有助于我们理解古土壤和土壤成因碳酸盐沉积的分布和保存，以及它们作为古环境和古气候监测的有用性(或局限性)。这些结果与预测地球岩石圈和生物圈对大气二氧化碳显着变化的响应的模型有关。

9418183 Mora The proposed research investigates changes in paleosol and pedogenic carbonate morphology and geochemistry preserved during the Siluro-Devonian time period, a period of rapid evolution and diversification of terrestrial ecosystems. Land plant evolution led to progressively more robust plant size and deeper rooting capabilities and more widespread afforestation of the land surface. The development and increasing abundance of vascular land plants may have contributed to increased weathering rates and draw down of atmospheric pCO2 from very high levels in the middle Paleozoic to near-present day levels in the Permo-Carboniferous. The proposed research will evaluate the hypothesis that afforestation, increased weathering profiles and also contributed to changes in the stable isotope composition of pedogenic carbonate. The proposed study will emphasize morphological and geochemical analysis of Siluro-Devonian paleosols from ten stratigraphic units (chiefly red-beds) exposed in outcrop in the U.S. and maritime Canada Appalachians. Detailed macro- and micromorphological characterization of the paleosols, estimation of paleosol thickness, mass balance evaluation of soil major and trace element geochemistry and stable isotopic analyses of pedogenic carbonates phases will be combined with existing paleontological information for these units to characterize the "pedological signature" of afforestation of the land surface by vascular plants. The results will permit a detailed evaluation of atmospheric pCO2 during this period of profound change using Cerling's soil carbonate paleobarometer. The results will contribute to our understanding of the distribution and preservation of paleosols and pedogenic carbonate deposits and their usefulness (or limitations) as monitors of paleoenvironments and paleoclimate. The results are relevant to models which predict the response of the Earth's lithosphere and biosphere to significant changes in atmospheric pCO2.