Место издания:Volgograd State University Volgograd
Первая страница:24
Последняя страница:25
Аннотация:Loess formations are loesses, loess-like rocks and related to them paleosoils that form loess-soil complexes (LSC). Lithologically LSC correspond to sedimentary-eolian cyclites. In which there are two stages: ascending, progressive (sedimentation) and descending, regressive (weakening of the dynamic of the environment, following erosion with a development of a horizon of paleosoils).
While studying loess deposits, it is necessary to apply rational classification of small- and fine-grained rocks with taking into consideration the nomenclature of sandstones, siltstones and clay rocks of mixed granulometric composition [Frolov, 1992].
Microscopically they are weakly cemented siltstones with different amount of clay component (from 7-10 to 35%), with small admixture of sand material (<10%), with abundance of open pores due to the presence of contact cementation (where grains are juxtaposed) and film-type cementation of clay and clay-calcareous composition, sometimes weakly ferruginized. Their cementation took place at diagenesis stage often with following transformation during hypergenesis as a result of increasing humidity. Rock-forming in them cannot serve as a partitive barrier between the weathering and diagenesis processes, and from geological point of view they appear simultaneously at different levels of the sequence.
Based on the results of granulometric and mineralogic analyses there are clayiness “granulometric” and clayiness “mineralogic” have been determined. However, “granulometric clayiness” of rocks of LSC is higher by 2,4-28%, comparing to the data of mineralogical analysis due to the presence of finely-dispersed particles of carbonaceous, sulphate and other compositions, which was pointed out by many researches.