Micromorphology, clay mineralogy, and geochemistry of calcic-soils from western Thar Desert: Implications for origin of palygorskite and southwestern monsoonal fluctuations over the last 30 ka

Abstract The Thar desert with intense aeolian activity and calcrete formation is one of the hottest arid regions of the world. Little is known about the formation of calcic soils with a large amount of palygorskite in the western Thar. In this study, we have used microscopy, sub-microscopy, clay mineralogy, and geochemistry of three calcic soils from western Thar to understand the pedogenesis in response to fluctuating southwestern monsoon over the last 30 ka. Thin sections of the soils show a dominance of weakly developed pedofeatures with powdery to well-indurated pedogenic calcium carbonate that influenced weathering of primary mineral grains. Sub-microscopy of the calcretes shows a large amount of fibrous palygorskite in pore spaces of micritic and sparitic nodules. XRD of the total clay (