Micromorphological and mineralogical features of saline playa surface sediments from two large Trans-Uralian lakes

The proposed paper is devoted to the features of mineralogical composition and microstructure of saline playa surface sediments from two large drainless lakes in the south west of Western Siberia. The material composing the surface sediments of both playas is an unlithified mixture of clay and sand, with a significant admixture of organic matter. Coarse material is represented mainly by quartz, with an insignificant admixture of feldspar grains and micaceous fragments. In general, terrigenous component is characterized by a comparatively low degree of sorting. Clay material is scarce and composed, presumably of chlorite-hydromica material with a significant admixture of undecomposed organic matter, and traces of ferruginization. Carbonates and evaporates are the most common authigenic minerals. In both cases carbonates occur as microconcretions that correspond to the zone enriched with cysts, plant detritus and other degrading organic matter. Evaporates occur both as the efflorescence on the surfaces of the crusts. The study results have shown that surface crusts contain zones enriched with Artemia salina cysts, which are a significant component of sediments. Degrading crusts promote secondary mineral formation, especially formation of carbonates. Surface crusts of two studied playa environments differ in proportion of terrigenous material, clay minerals, as well as the composition of evaporates and carbonates.