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首页> 外文学位 >The production and evolution of mobile regolith: Modeled soil production and measured chemical weathering.
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The production and evolution of mobile regolith: Modeled soil production and measured chemical weathering.

机译：流动碎屑的产生和演化：模拟土壤产量和测量化学风化作用。

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摘要

Physical and chemical processes operate to release material from intact, immobile rock and render it susceptible to downslope transport. The transformative processes that create mobile material (soil or regolith) can exert control on landscape evolution in actively eroding, rock-dominated landscapes. This study examines rates of soil production in a variety of landscapes and the chemical evolution of mobile material on two granitic hillslopes.;Steady landscapes should display convex hilltops with uniform soil thickness and rates of release from the soil-bedrock interface. A hillslope at Bodmin Moor, UK displays parabolic hillslope form; however, depths to bedrock and soil production rates exhibit variability. We develop a theory of block-by-block lowering of the soil -- bedrock boundary, supported by a modeling exercise, to explain this inconsistency. Over long timescales a hillslope can be in steady state while at any point in time exhibiting a range of depths to bedrock.;We introduce a new soil production model that predicts rates of soil production by fitting published rates derived from in situ cosmogenic radionuclide data from different landscapes. The new model predicts soil production based on a variety of field parameters including precipitation and rock type to better account for the variability of soil production at different localities.;As material moves downslope, chemical weathering and mixing processes contribute to its evolution. We examine chemical and mineralogical data to quantify transformations that have occurred on two granitic hillslopes: Osborn Mountain, USA and Bodmin Moor, UK. The sites have experienced different temperature and moisture conditions throughout their history, with Osborn Mountain remaining cool and dry compared to Bodmin Moor. Our results indicate that temperature and water availability influence the mineralogical and chemical transformations that occur as material weathers.;We compare solid-phase and soil pore-water chemistry data from Bodmin Moor to elucidate chemical transformations. We use the chemical speciation model, PHREEQC, to show that conditions are favorable for secondary mineral precipitation below the soil O-horizon. The data are coupled with residence times to compute long-term and contemporary weathering rates. Contemporary rates of weathering are higher than the long-term average for a majority of chemical constituents.
机译：物理和化学过程的作用是从完整的固定岩石中释放出材料，并使之易于下坡运输。产生可移动物质（土壤或重石块）的转化过程可以控制主动侵蚀，以岩石为主的景观中的景观演化。这项研究检查了各种景观中土壤的生产率以及两个花岗岩山坡上的可移动物质的化学演化。稳定的景观应显示出具有均匀土壤厚度的凸起山顶和从土壤-基岩界面释放的速率。英国博德明高地的山坡呈抛物线形。然而，基岩的深度和土壤生产率显示出可变性。我们开发了一种逐块降低土壤的理论-基岩边界，并通过建模练习来解释这种不一致之处。在很长的时间范围内，山坡可以处于稳定状态，而在任何时间点上都具有一定范围的基岩深度。我们引入了一种新的土壤生产模型，该模型可以通过拟合从原位宇宙成因放射性核素数据得出的已公布的速率来预测土壤的生产率不同的风景。新模型根据包括降水和岩石类型在内的各种田间参数来预测土壤产量，以更好地说明不同地区土壤产量的变化性。随着物料向下坡移动，化学风化作用和混合过程有助于土壤演化。我们检查化学和矿物学数据，以量化在两个花岗岩山坡上发生的转变：美国奥斯本山和英国博德明高沼。这些遗址在整个历史过程中经历了不同的温度和湿度条件，与博德明高沼相比，奥斯本山保持凉爽干燥。我们的结果表明温度和水的可利用性会影响随着材料天气而发生的矿物和化学转化。;我们比较了Bodmin Moor的固相和土壤孔隙水化学数据，以阐明化学转化。我们使用化学形态模型PHREEQC来表明条件对土壤水平以下的次生矿物沉淀是有利的。数据与停留时间相结合以计算长期和当代的风化率。对于大多数化学成分，当代的风化率高于长期平均水平。

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  • 作者

    Riggins, Susan Gardner.;

  • 作者单位

    University of Colorado at Boulder.;

  • 授予单位 University of Colorado at Boulder.;
  • 学科 Geomorphology.;Geochemistry.
  • 学位 Ph.D.
  • 年度 2010
  • 页码 199 p.
  • 总页数 199
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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