Mineralogy and Geological Significance of 14 Intergrade Clays in Soils

The 14 intergrade clay is one of the most common soil derived clay species produced during pedogenesis process.It documents the climate and environmental conditions of the period and also can be used as the criteria for soil genesis and classification.In this paper,previous studies on 14 intergrade clay from literature are summarized,and its mineralogical characteristics,interlayer components,identification criteria,and genesis are clarified.The identification flow chart for 14clay species is proposed based on the reviews of the intergrade clay species.In addition,high-resolution transmission electron microscopy(HRTEM) provided the powerful tool for intergrade clay investigation.Formation mechanism of intergrade clays could be investigated through HRTEM observation.This 14 intergrade clay is sensitively to climate and environmental conditions during the pedogenesis episode,especially the acidity of soils.Therefore,this intergrade clay species is a potential probe to the climate and environmental conditions of the pedogenesis period.