Mineralogical Studies of Benchmark Soils of Darjeeling Himalayas and Tarai Region of West Bengal Maurya U.K.1, Sarkar Dipak2, Nayak D.C.2 1Division of Soil Resource Studies, National Bureau of Soil Survey and Land Use Planning, Amravati Road, Nagpur - 440 010, India. 2National Bureau of Soil Survey and Land Use Planning, Sector II, Block-DK, Salt Lake, Kolkata-700091, India. Abstract Three Benchmark soils developed from gneisses/schists, sandstone, siltstone and shale in high altitude of Darjeeling Himalayas and Tarai region of West Bengal respectively, were studied for their chemical and mineralogical properties. Soils are shallow to deep, pale brown to dark brown in colour and coarse to moderately fine textured, acidic, high in organic carbon and low in CEC and base saturation. Heavy mineral suit was dominated by opaque followed by pyroxene, hornblende, biotite, tourmaline, kyanite, sillimanite, phlogopite and staurolite. Some of these mineral grains show etching and alteration features. The 001/002 ratio of 1.0 nm peak of silt mica was more than 2 and remain constant with depth, indicating enrichment of soils with di- and trioctahedral micas. The mineralogy of the clay fraction is dominated by mica followed by kaolin, chlorite, vermiculite and gibbsite with minor amounts of smectite and feldspars. The 0.7nm peak indicates that it is not a discrete kaolinite but interstratified with 2: 1 minerals. The presence of gibbsite in these soils is not a part of contemporary pedogenesis. Top |