Coupling uranium series and ¹⁰Be cosmogenic radionuclides to evaluate steady-state soil thickness in the Betic Cordillera

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• 作者：Jé ; rô ; me Schoonejans^a ; ^{jerome.schoonejans@uclouvain.be" class="auth_mail" title="E-mail the corresponding author} ; Veerle Vanacker^a ; ^{veerle.vanacker@uclouvain.be" class="auth_mail" title="E-mail the corresponding author} ; Sophie Opfergelt^b ; ^{sophie.opfergelt@uclouvain.be" class="auth_mail" title="E-mail the corresponding author} ; Mathieu Granet^c ; ^{mgranet@unistra.fr" class="auth_mail" title="E-mail the corresponding author} ; Franç ; ois Chabaux^c ; ^{fchabaux@unistra.fr" class="auth_mail" title="E-mail the corresponding author}
• 关键词：U-series isotopes ; Soil production rate ; 10Be derived denudation rates ; Semi-arid environment ; Soil development ; Steady state soil thickness
• 刊名：Chemical Geology
• 出版年：2016
• 出版时间：23 December 2016
• 年：2016
• 卷：446
• 期：Complete
• 页码：99-109
• 全文大小：1943 K

文摘

On Earth, the Critical Zone is the near-surface environment where interactions between the atmosphere, lithosphere, hydrosphere and biosphere take place. The development of the regolith mantle is controlled by the downwards propagation of the weathering front into the bedrock and denudation at the surface of the regolith by mass movements, water and wind erosion. When the removal of surface material is approximately balanced by the production of weatherable material at the bottom of the regolith profile, the soil system is assumed to be in steady-state. Although recent literature on chemical weathering often assumes that soils have a steady-state thickness, the concept has rarely been validated with empirical field data. In this study, we present and compare analytical data from two independent isotopic techniques: in-situ produced cosmogenic nuclides and U-series disequilibria to constrain soil development under semi-arid climatic conditions. Three soil profiles were sampled across the Betic Ranges, at the ridge crest of zero-order catchments with distinct topographic relief, hillslope gradient and ¹⁰Be-derived denudation rate. Soil production rates determined based on U-series isotopes (²³⁸U, ²³⁴U, ²³⁰Th and ²²⁶Ra) are of the same order of magnitude as ¹⁰Be-derived denudation rates, suggesting steady state soil thickness, in two out of three sampling sites. Our results show the potential of a combined U-series disequilibria and in-situ ¹⁰Be isotope approach to evaluate steady-state soil thickness. Our study also illustrates the frontiers in applying U-series disequilibria to track soil production in environments characterized by weak soil development.