Origin of the Calcrete Deposits of Saswad-Nira Area, Western Maharashtra, India

Extensive development of calcrete deposits is observed in the Saswad-Nira area of western Maharashtra. Calcrete occurs in a variety of forms, the most common being powder, nodular, laminar, platy, tubular and hardpan calcretes. The DTA, XRD and IR spectroscopic studies show that the calcretes are composed chiefly of micrite - a microcrystalline calcite. Dolomite and opaline silica occur in subordinate amounts. The clay fraction of calcretes is dominated by attapulgite (palygorskite) and sepiolite, which along with other interlayer clay minerals like chlorite-montmorillonite and illite-montmorillonite, indicate extreme alkaline conditions for the precipitation of calcretes. The chemical data reveal that apart from calcium carbonate, silica and magnesium carbonate constitute an appreciable portion of some calcrete samples. From the textural, mineralogical and chemical characters of calcretes, it is evident that the precipitation of calcium carbonate in vadose zone and its progressive accumulation in the soils has ultimately resulted in the development of extensive calcrete deposits.