Duricrust

Duricrust is a collective term for a hardened horizon within or at the surface of weathered soil or regolith, formed by the cementation of loose material through minerals precipitated from groundwater. These crusts arise when chemical weathering products are mobilized by percolating water, then concentrated and cemented near or at the surface. They commonly occur in tropical and arid to semi-arid environments, where evaporation concentrates solutes and groundwater moves laterally or upward, creating durable layers that can range from thin crusts to thick, coherent bands. Duricrusts can impair root penetration, reduce infiltration, and influence landscape uplift and soil drainage, with implications for agriculture and engineering.

Common types and cementing agents include ferricrete (iron oxide or hydroxide cementation), calcrete or calcicrete (calcium carbonate cementation), silcrete (silica cementation), aluminous duricrusts (aluminum oxides/hydroxides), and gypcrete (gypsum cementation). The relative abundance of oxides, carbonates, silica, or sulfates reflects climate, vegetation, and the source rock. Formation processes involve leaching of mobile ions from overlying material, evaporation and concentration of solutes, and subsequent precipitation that cements particles together.

Duricrusts have a wide geographic distribution, notably in Australia, parts of Africa, India, and the Americas. They influence soil fertility, hydrology, and land-use planning, and are significant in mineral and groundwater exploration because their chemistry and texture reflect weathering intensity and groundwater regimes.