Pedogenic accumulations of crystals and nodules of gypsum are common in desert soils, especially extreme deserts such as the Atacama Desert, Chile. Some soils with both pedogenic gypsum and calcite have the gypsic (By) horizon below the calcic (Bk) horizon. Here we present a compilation of 88 gypsic soils from around the world to derive a relationship (R2 = 0.63, standard error = ±129 mm) between depth to the By horizon (D, in centimeters) and mean annual precipitation (P, in millimeters) as follows: P = 87.593e0.0209D. This relationship can be used to derive paleoprecipitation estimates from paleosols, once depth to the gypsic horizon is corrected for compaction due to overburden. Application of this technique to Early Permian paleosols near Gilliland, Texas, confirms paleoprecipitation estimates in the same sequence derived from depth to the calcic horizon. Barite is another sulfate mineral that forms nodular horizons in paleosols, but not in modern soils. Miocene paleosols in Panama with both calcareous and barite nodules suggest that this weakly soluble salt forms at levels in paleosols unlike those of either pedogenic carbonate or gypsum.

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