ИСТИНА

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). 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. In mineral composition of LSC following components are destinguished: allothigenic, brought from outside (of quartz-silicate, alumosilicate and partially of calcareous composition), and authigenic, formed in the place. Amongst newly formed components there are clay minerals and their mixed mineral phases, less common zeolites, and also carbonates (calcite, dolomite), rarely sulphates (gypsum), and partly sulfides and iron oxides (pyrite and goethite), and phosphates (vivianite). 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.