Paleosol

A soil formed in the past and preserved in the geological record, commonly buried beneath younger sediments. Its layers and chemical features record ancient surface conditions.

Soil horizon: A roughly horizontal soil layer distinguished by its composition, color, or structure. Horizon sequences preserve the layered profile used to identify a paleosol.
Paleoclimate: The climate conditions of a period before direct instrumental measurements were available. Paleosol minerals and chemical signatures can indicate ancient temperature and rainfall.
Caliche: A hardened soil layer or crust enriched in calcium carbonate, commonly formed in arid or semiarid settings. Ancient caliche horizons are paleosols that can indicate prolonged soil formation under dry conditions.
Illuviation: The downward movement and accumulation of dissolved or suspended materials within a soil profile. Accumulated clay or iron can form diagnostic horizons in a paleosol.
Paleosol carbonate method: A method for estimating ancient atmospheric carbon dioxide from carbon isotopes in soil carbonate nodules. Its estimates depend on assumptions about soil respiration, temperature, and carbonate formation.
Soil profile: A vertical section through soil showing its horizons from the surface downward. A preserved profile reveals how soil-forming processes varied with depth.
Paleobotany: The study of fossil plants and plant remains from geological history. Root traces and organic matter in paleosols preserve evidence of ancient vegetation.
Laterite: A soil or rock enriched in iron and aluminum oxides by intense weathering and leaching. Lateritic paleosols preserve evidence of strong chemical weathering in ancient landscapes.
Pedoturbation: The mixing of soil by organisms, roots, shrinking and swelling, or other physical processes. Mixing blurs horizons and modifies structures before or after burial.
Pedogenic carbonate: Carbonate minerals formed or accumulated in soil through soil-forming processes. Distinguishing primary soil carbonate from later carbonate is essential to reliable paleoclimate interpretations.

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