The critical role of climate and saprolite weathering in landscape evolution
The critical role of climate and saprolite weathering in landscape evolution
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DOI：
10.1002/esp.1836
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发表时间：
2009-09-15
影响因子：
3.3
通讯作者：
Amundson, Ronald
中科院分区：
文献类型：
--
作者：
Dixon, Jean L.;Heimsath, Arjun M.;Amundson, Ronald
地貌的演变是对影响侵蚀和风化的表面过程的外部力量的反应，如构造和气候。侵蚀和风化之间的内部反馈在调节景观响应方面也起着不可或缺的作用。我们对这些内部和外部反馈的理解仅限于少数基于实地的研究，其中只有少数明确研究了腐岩风化。在这里，我们报告的腐泥土和土壤的侵蚀和风化率，以量化气候如何影响剥蚀，通过集中在西塞拉利昂内华达州山脉，加州的海拔样带。我们使用一个适应的质量平衡的方法和夫妇的宇宙成因放射性核素（CRN）Be-10与岩石，腐泥土和土壤中的锆浓度的土壤生产率。我们的方法包括深层腐岩风化，并表明以前的研究可能低估了类似景观的剥蚀率。沿着所研究的气候梯度，化学风化速率在中海拔（1200-2000 m）达到峰值，平均为112.3 +/- 9.7 t km（-2）y（-1），而高海拔和低海拔地区为46.8 +/- 5.2 t km（-2）y（-1）。测得的风化率遵循类似的模式与气候的预测二氧化硅通量，建模使用Arrhenius温度关系和通量和降水之间的线性关系。此外，化学风化和侵蚀在我们的场地中密切相关，物理侵蚀率随着腐泥土风化率和强度的增加而增加。出乎意料的是，腐泥土和土壤风化强度呈负相关，这样更多的风化腐泥土被弱风化土壤覆盖。这些数据量化了气候、风化和侵蚀之间令人兴奋的联系，并共同表明气候通过温度和湿度控制化学反应速率来控制化学风化。我们的研究结果还表明，腐泥土风化降低基岩的连贯性，导致更快的土壤运输速度，反过来，减少材料在土柱中的停留时间，限制土壤风化。版权所有（C）2009约翰威利父子有限公司
Landscapes evolve in response to external forces, such as tectonics and climate, that influence surface processes of erosion and weathering. Internal feedbacks between erosion and weathering also play an integral role in regulating the landscapes response. Our understanding of these internal and external feedbacks is limited to a handful of field-based studies, only a few of which have explicitly examined saprolite weathering. Here, we report rates of erosion and weathering in saprolite and soil to quantify how climate influences denudation, by focusing on an elevation transect in the western Sierra Nevada Mountains, California. We use an adapted mass balance approach and couple soil-production rates from the cosmogenic radionuclide (CRN) Be-10 with zirconium concentrations in rock, saprolite and soil. Our approach includes deep saprolite weathering and suggests that previous studies may have underestimated denudation rates across similar landscapes. Along the studied climate gradient, chemical weathering rates peak at middle elevations (1200-2000 m), averaging 112.3 +/- 9.7 t km(-2) y(-1) compared to high and low elevation sites (46.8 +/- 5.2 t km(-2) y(-1)). Measured weathering rates follow similar patterns with climate as those of predicted silica fluxes, modeled using an Arrhenius temperature relationship and a linear relationship between flux and precipitation. Furthermore, chemical weathering and erosion are tightly correlated across our sites, and physical erosion rates increase with both saprolite weathering rates and intensity. Unexpectedly, saprolite and soil weathering intensities are inversely related, such that more weathered saprolites are overlain by weakly weathered soils. These data quantify exciting links between climate, weathering and erosion, and together suggest that climate controls chemical weathering via temperature and moisture control on chemical reaction rates. Our results also suggest that saprolite weathering reduces bedrock coherence, leading to faster rates of soil transport that, in turn, decrease material residence times in the soil column and limit soil weathering. Copyright (C) 2009 John Wiley & Sons, Ltd.