Division of Soil Science and Agricultural Chemistry, Indian Agricultural Research Institute, New Delhi, 1100l2.
Present address:1 Department of Soil Science, Assam Agricultural University, Jorhat, 785013.
Fine sand mineralogy of the soils of lower Brahmaputra valley zone of Assam was dominated by quartz (41.0~1.3%), orthoclase (27.6–39.2%), plagioclase (1.8–6.3%) and muscovite (9.3–25.8%) in the light fraction and zircon (19.0–34.3%), biotite (23.2–29.3%), chlorite (19.6–31.4%), hypersthene (0–8%) and kyanite (2.2–7.2%) in the heavy fraction. The light mineral fraction constituted 89.7–99.9 per cent of the fine sand fraction. The mineralogical suit indicates that parent materials of the soils are derived from sedimentary and partially metamorphosed rocks. The weathering ratio (Q/F) indicated more weathering of feldspars in the surface horizons.
Sand mineralogy, sedimentary, metamorphic, weathering ratio
