Sedimentary minerals that reliably record past arid climates are those that form where evaporation outpaces water input and where soil processes concentrate soluble elements. Field and laboratory studies by recognized sedimentologists link specific mineral assemblages to drying environments, but interpretation requires attention to preservation and diagenesis.
Evaporites: halite, gypsum, anhydrite and soluble salts
Evaporites such as halite, gypsum, and anhydrite are the classic indicators of strong evaporation and basin restriction. John K. Warren University of Adelaide has reviewed how thick salt and sulfate sequences form in settings with minimal freshwater inflow and sustained evaporation, making them primary evidence for aridity in marine and continental basins. These minerals record water chemistry and hydrologic balance rather than temperature, so their presence signals evaporative concentration and often closed-basin conditions. Diagenetic replacement and burial can alter textures and convert gypsum to anhydrite, so petrographic and geochemical checks are essential before interpreting climate.
Pedogenic carbonates, calcrete and authigenic nitrates or borates
Pedogenic carbonates and calcrete horizons in soils form where evaporation and limited leaching drive carbonate precipitation in the vadose zone. Greg Retallack University of Oregon has shown calcrete profiles in paleosols correlate with seasonally arid to semi-arid climates and provide records of soil moisture and vegetation change. Stable carbon and oxygen isotopes in these carbonates, as documented by Timothy E. Cerling University of Utah, offer quantitative constraints on aridity and plant types because isotopic composition reflects soil CO2 sources and evaporation. In hyperarid regions, accumulation of soluble salts such as nitrates and borates also points to negligible rainfall and limited groundwater flushing; Chilean nitrate-bearing sediments in the Atacama Desert exemplify extreme aridity shaping both landscape and human economy.
Interpreting these mineral proxies requires integrated evidence. Petrography, mineralogy, and geochemistry together distinguish primary evaporites from later introduced salts and separate pedogenic carbonates from marine limestones. Territorial and cultural contexts matter because arid mineral deposits often control water availability, agriculture, and historical settlement patterns, and modern land use can overprint ancient soil signals. Environmental consequences include high preservation potential for evaporites in closed basins and, conversely, loss of soluble indicators where later humidization leaches salts. When multiple mineral indicators align, and when authoritative sedimentological work such as that by Warren, Retallack, and Cerling is applied, the sedimentary mineral record provides robust evidence for past arid climates.