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首页> 外文期刊>Soil Horizons >Freeze-agglomeration: an alternative mechanism for clay film formation.
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Freeze-agglomeration: an alternative mechanism for clay film formation.

机译：冻结凝聚：粘土膜形成的另一种机制。

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摘要

Oriented clay coatings (argillans, clay cutans, clay films, lamellae) are often interpreted to be caused by illuviation (pervection, lessivage) of fine clay particles. In montane meadow soils (Typic Humaquepts) of the northern Sierra Nevada Range, prominent clay cutans occur on ped faces of a paleosol 3Btgb horizon, which is contemporaneous or younger than 2840+or-220 yr BP by radiocarbon dating. The unlikelihood of distinct clay cutans forming in such a short period of time via illuviation in a soil with an aquic moisture regime suggests an alternative mechanism. Laboratory studies show that silt- and sand-sized agglomerates can be produced by subjecting colloidal kaolinite (high Fe content), extracted from the montane meadow soil, to repeated freeze-thaw cycles. These agglomerates have a distinct microgranular texture and one to several birefringent domains. Thin section microscopy of the surface Oa horizon reveals that pores and root channels are coated by oriented birefringent zones resembling clay cutans. These clay cutans are similar in optical properties to laboratory-produced freeze-agglomerates. Optical microscopy of clay cutans, scraped from the paleosol 3Btgb horizon, suggests that they too may have formed via freeze-agglomeration. Freeze-agglomeration is proposed as a new mechanism to produce oriented clay films.
机译：定向的粘土涂料（argillans，粘土cutan，粘土膜，薄片）通常被认为是由细粘土颗粒的照射（渗透，疏松）引起的。在内华达山脉北部的山地草甸土壤（典型的湿地）中，在3Btgb地平线古土壤的带脚面上出现了显着的粘土角砾岩，根据放射性碳测年，该古土壤同时或小于2840+或-220 yr BP。在具有含水水分的土壤中通过照射在短时间内形成的独特粘土角质岩不太可能显示出另一种机制。实验室研究表明，通过对从山地草甸土壤中提取的胶态高岭石（高铁含量）进行反复的冻融循环，可以生产出粉沙大小的附聚物。这些附聚物具有独特的微颗粒结构和一个至几个双折射域。表面Oa层的薄切片显微镜显示，孔和根通道被类似于粘土角质的定向双折射区覆盖。这些粘土角质胶的光学性质与实验室生产的冷冻附聚物相似。从古土壤3Btgb层刮下的粘土角质的光学显微镜表明，它们也可能是通过冷冻凝聚形成的。提出了冷冻结块作为生产取向粘土膜的新机制。

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