Classification Of Saline Soil With Salt Crust In Playa Region Of Lop Nur "Great Ear"

During the first and the second national soil investigations, Lop nur was not consideredas consisting of soils, which means salt crust was not soil but salt deposit. However, deposit inplaya region should be considered as a special saline soil form soil genesis perspective. Nosystematic research was carried out on salt deposit using pedology principles so far. Thus,study on soil genesis and classification of saline soil with salt crust in playa region of Lop nur“Great Ear” may offer some revising suggestions for classifying saline soils in Chinese soilgenesis classification. This research may offer some revising suggestions for classifyingsaline soil in Chinese soil genesis classification and Halosols in Chinese soil taxonomicclassification. Furthermore, the blank of soil geology research in this area may be filled up bycompiling medium scale soil maps in this region. Global change is currently a hot researchtopic. Interpretation of soil memory information may help us reconstructing pastenvironmental change, especially paleo-environment change during the past2000years.In this study, traditional soil geography research was used as the basic method, and salinesoil with salt crust in playa region of Lop nur “Great Ear” was selected as the researchmaterial. Results on geology, geography, and archaeology in Lop nur region from formerscientists were collected. Using remote sensing image in the study area as base map, andcombined with indoor interpretation results and traditional point layout approach, soil profilesites were selected. Soil samples were collected after differential GPS positioning in field, soilphysico-chemical properties were analyzed indoor. Profile horizons characteristics, materialconstitution and forming time of saline soil with salt crust in the playa region of Lop nur“Great Ear” were investigated in this study. Main conclusions involve:Firstly, salt crust in playa and salt crust in soil are two different types of salt crusts,which represent different soil forming environments. Formation of salt crust in soil in inlandarid regions mainly related with saline dive at high water level. However, salt in salt crust inplaya was formed by crystallization when salt in lake was supersaturated and, salt crust inplaya experienced three stages, i.e., saline lake, salt lake, and playa.Secondly, salt content of salt crust in playa was normally larger than80%, while that ofsalt crust in soil was usually less than20%. Therefore, salt crust in playa was very hard, and cracks were formed during shrinking process. Texture images could be detected.Thirdly, Characteristics such as10-20%silt and sand content in salt crust, and thinhorizon consisted of silt and sand, proved that wind in arid desert area was an importantsoil-forming factor. Accumulation of wind dust was a long process. High silt dust content insalt crust also illustrated that salt crust could not be formed in short period in “Great Ear”region.Fourthly,14C result at the bottom mucky layer of the profile showed that saline soil withsalt crust in the Lop nur “Great Ear” region was formed since the middle of Holocene.Fifthly, suggestions on revising Chinese Soil Taxonomy Classification were offered, bystrictly defining salt crust in playa horizon. In Chinese soil genesis classification, a newsubgroup, i.e., saline soil with playa salt crust, should be included in saline soil group. InChinese soil taxonomic classification, a new subgroup, i.e., Playa salt crust Ari-OrthicHalosols should be included in Ari-Orthic Halosols group.