The Identification Of Paleosol Types In Fenghuangshan Reference Profiles In Liaoning Chaoyang,China

It is well known that the thick loess which is widely-distributed in the north of China was formed over a long period of deposition. The paleosols in this loess were superimposed and have different colours. After erosion in this hilly region, deep buried paleosols at different pedogenetic stages were exhumed and exposed at the ground surface. Different paleosol types at various buried depths were exposed at the surface as a result of intense erosion; differences in depth of eroded soil have resulted in a variety of soil types developed in different climatic zones within a small area. This poses challenges to the recognition, classification and mapping of soils. There are thus merits in establishing reference profiles in different ecological areas to aid the recognition and classification of paleosols.In this soil study we introduce the concept of a stratigraphic section as used in geology. A paleosol reference profile which demonstrates well preserved stratigraphic sections including various paleosols types, was established in Chaoyang city, Liaoning province of China. The origin, ages, rates of deposition, sedimentary continuity, and basic physical and chemical properties of the paleosol reference profile were: examined. Furthermore, the soil formation processes of the soil derived from Quaternary loess were also revealed. On the basis, selecting4layers of Paleosol and4layers of loess from the reference profile(was19.85metres in depth, below2.28m formed by wind deposition, has been deposited continuously since423ka BP), a total of34soil layers.Soil samples from22profiles developed in different climatic regions from south to north of China were collected and analyzed to assist with recognizing and classifying paleosols.Finally, taking the soil profile as the object classification factors, the red index, CIA, free degree of iron, iron activation degree, mean annual temperature, annual precipitation as the clustering factors, through cluster analysis, to objectively determine the ancient soil types in each period.The findings from this study illustrate that the deposition of widely-distributed thinner and finer loess synchronized with pedogenic processes and thus multi-layered paleosols associated with the alternation of dry-humid and hot-cool cycles appeared in the thick loess profiles which formed during the long period of sedimentation. The loess layers buried at depth should be included in the paleosol category. Therefore, only classifying red soil as a paleosol is inappropriate.Through laboratory analysis, the results:Soil color of the paleosol reference profile (dry) is7.5YR-2.5YR, apparently the profile contains a lot of hematite;The S1-2:RR value ranges from7.5to12, the average value is10.25;L2:RR value is7.5;S2:RR value is7.5; The L3:RR value ranges from4.3to7.5, the average value is5.4;S3:RR value is12; The L4:RR value ranges from1.9to7.5, the average value is3.7.S4:RR value ranges from4.3to13.3, the average value is8.6;L5:RR value ranges from6.4to7.5, the average value is7.1.There is a negative correlation between iron oxide of Fenghuangshan reference profile and pH value of iron oxide-activated water system.In Fenghuangshan,ancient soil base strata chemical weathering degree:L4<L2<L3<L5<Si.2<S2<S4<S3; Xiang-01<S3<Wan-O3, Yu-03<S1-2<S2<S4<E-01, Su-01<L5<Yu-03, L3<E-03, Liao-01<L4<L2<Su-02.pH value of Fenghuangshan ancient soil was all above7.35, the ancient iron in soil mobility is relatively weak, resulting in different iron enrichment degree:ancient soil (red)> loess paleosol> local zonal soil (Liao-02).The iron content of ancient soil profile (red) change from63.75g·kg-1to67.04g-kg-1, in Loess it changes from57.59g-kg-1to61.29g-kg-1, were all higher than that of zonal soil (Liao-02),iron content in cinnamon soil was52.32g-kg-1.Fenghuangshan region and its source region in S4period (311-403Ka BP) had a relatively stable climate and strong continental chemical weathering characteristics, L4period (243～311Ka BP) had the characteristics of relatively stable climate environment and weak continental chemical weathering characteristics.Through referring to the soils developed in different climatic regions, this study suggests that the paleosol types in the reference profile involved red soil (hapludults in US Soil Taxonomy), yellow-cinnamon soil (ferrudalfs), brown soil (hapludalfs) and cinnamon soil (haplusalfs). The climatic conditions influencing the formation of these paleosols were a subtropical humid, a northern subtropical climate, a humid temperate climate and a temperate semi-arid climate, respectively. The results provide the basis for an understanding of soil formation and classification in this region as well as for soil mapping and management in loess hilly regions.