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

[9418183] Mora本研究探讨了古土壤和成土碳酸盐形态和地球化学的变化，这是一个陆地生态系统快速进化和多样化的时期。陆地植物的进化导致植物体积逐渐增大，生根能力逐渐加深，地表造林面积逐渐扩大。维管陆生植物的发育和丰度的增加可能促进了风化速率的增加，并使大气中的二氧化碳分压从古生代中期的很高水平降低到二叠纪-石炭纪的近现代水平。提出的研究将评估植树造林，增加风化剖面，也有助于改变成土碳酸盐的稳定同位素组成的假设。本研究将着重对美国和加拿大沿海阿巴拉契亚地区露头的10个地层单元（主要是红层）的志留纪-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、古土壤厚度估算、土壤主要和微量元素地球化学质量平衡评价以及成土碳酸盐相稳定同位素分析将与这些单元的现有古生物信息相结合，以表征维管植物造林的“土壤学特征”。结果将允许使用Cerling的土壤碳酸盐古气压计对这一深刻变化时期的大气二氧化碳分压进行详细评估。这些结果将有助于我们了解古土壤和成土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用途（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分压显著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.