Minerals, plasmic fabrics and clay pedofeatures in Vertisols with and without soil modifiers (zeolites)

Abstract

One zeolitic Vertisol front semi-arid (dry) and the other non-zeolitic Vertisol from semi-arid (moist) climatic zones viz., Jhalipura in Rafashihan and Bhatumbra in Karnataka, respectively were studied for their micromorphological characteristics. The Jhalipura soils exhibited weak plasma separation with mosaic speckled and undifferentiated b-fabric. They consisted of both non-pedogenic carbonates (NPC) and pedogenic carbonates (PC). Zeolites were predominantly observed in the soil matrix. In addition, muscovite, quartz, few tiny grains of zircons and tourmalines have also been identified Elongated voids, septaric carbonate nodules with epicoating of PCs and shearing (off set) in channel voids and stress oriented clay pedqfeatures were prominently observed. In contrast, Bhatumbra soils showed strong plasma separation with distinct zoning and exhibited parallel striated, porostriated and granostriated b-fabric. The soils have more NPCs than PCs. Non-clay minerals such as quartz, plagioclase feldspar, muscovite, biotite and heavy minerals such as zircon and tourmaline are also present. Few black carbonate nodules are only present in the coarser fraction of Bhatumbra.soils. Weak plasmic separation and mosaic speckled and undifferentiated plasmic fabric in Jhalipura soils may be because of less shrink-swell activity and also because of high amthint of zeolites studded in the matrix, whereas strong plasmic separation and strongly oriented plasmic fabric in Bhatumbra soils may have resulted due to high clay activity and also due to high stress related to shrink-swell potential of clay. Slightly higher amount of PC's in Jhalipura may be because of the dry pedoenvironment. The presence of zeolites in the soils of Jhalipura is attributed to their parent material (atnygdolnidol basalt). Presence of elongated voids and shearing in channel voids were observed only in Jhalipura soils and this may be due to the stress generated by non-pedogenic processes.