Genetic and micromorphological studies of the Holoence soil complex on the southern Loess Plateau
黄土高原南部全新世土壤微结构形成机理探讨

Detailed soil micromorphological analysisin Holoence loess-palaeosol profile in southern Loess Plateau, along with comparisons withanother profile nearby, the thesis discusses the characteristics of weathering and forming processes. It indicates that the micro-texture ofthe Holoence loess-palaeosol sequence is divided into both cementing texture including type 1, type 2 and type 3, and granular textureincluding type 4, type 5 and type 6.Cementing textureisalways in the palaeosol layers and was formed in warm-humid forest environment. Granular textureisalways in typical loess layers or weathering loess layers and was formed in a dry environment. It has been discovered that the palaeosol S 0 is separated into two distinct types of soils, namely palaeosols S 02 and S 01, because of the deposition of a layer (L x) inthe aridness. Soil S 0 substantively is a polycyclic soilthat is composed of two layers interbedding a loess layer, with two remarkable soil-formingprocesses. The lower soil S 02 is brown palaeosol, with the strongest argillification and eluviation, and was formed in early soil-forming phase. Argillic horizons were identified in the soil S 02. The upper soil S 01 is leached cinnamon palaeosol, with distinct argillification and weak calcification, and was developed in late soil-forming phase. The polycyclic soilS 0indicates that pedogenic environment has distinct variations. Cover layer above the polycyclic soilS 0is not a manured aggradated layer because of continuously piling up of loessial dung. It is a loess layer because of accelerated aeolian dust deposit. The cover is divided into both lower loess L 0weakly disturbed by cultivation activities and upper plough horizon strongly disturbed by cultivation activities. It indicates that it has been a relative arid period after the ending of formation of palaeosol S 0, with clear northwestmonsoon domino effect andaccelerated aeolian dust deposit. The polycyclic soilS 0 has been buried and become palaeosol of the Holoence.