MICROMORPHOLOGICAL AND MINERALOGICAL DIAGNOSTICS OF POST-AGROGENIC EVOLUTION OF GYPSIC SALIC SOLONETZ IN THE NORTH OF THE CASPIAN LOWLAND, RUSSIA

References: 17th International Multidisciplinary Scientific GeoConference SGEM 2017, www.sgem.org, SGEM2017 Conference Proceedings, ISBN 978-619-7408-05-8 / ISSN 1314-2704, 29 June - 5 July, 2017, Vol. 17, Issue 32, 373-380 pp, DOI: 10.5593/sgem2017/32/S13.049

ABSTRACT

This paper presents macro- and micromorphological, mineralogical and physicochemical characteristics of solonetzic processes that developed within a 14-cm-thick plough (P) layer of non-ameliorated Solonetz over a 50-year-long period of its post-agrogenic evolution. These processes have resulted in the formation of a microporofile with micromorphological features of eluvial-illuvial differentiation within the former plough layer. The mineralogical analysis of particle-size fractions (˂1, 1–5, 5–10, >10 μm) of the post-agrogenic Solonetz shows that the clay fraction (˂1 μm) of loamy parent material is dominated by complex random-sequence mica/smectite minerals; other constituents in the order of decreasing proportions are hydromica, chlorite and kaolinite. The upper eluvial microhorizons (AJ1el and AJ2el, 0-3 cm) of the former P layer are characterized by a decreased content of clay fraction and most significant changes in its mineralogical composition: a relative decrease in the content of mica/smectite and relative increase in the content of finely dispersed quartz, plagioclases and potassium feldspars. The lower illuvial microhorizon (Psn,pa, 7-14 cm) of the former P layer is characterized by relatively increased contents of both clay fraction and mixed-layer mica/smectite components of this fraction. The differentiation observed within this microprofile is connected with decomposition of the clay minerals in the upper microhorizons and their migration/illuviation into the lower microhorizons. The data obtained on the mineralogical differentiation of the former plough layer of non-ameliorated Solonetz are indicative of initial stages of solonetzic process that has developed within this layer over a 50-year-long period of post-agrogenic soil evolution under conditions of increasing climate humidity.

Keywords: Solonetz, micromorphology, mineralogy, evolution.