# Citronelle Formation Canonical page: https://lithomap.app/resources/geologic-formations/united-states/citronelle-formation Last reviewed: September 17, 2026 Page purpose: Comprehensive United States geologic formation reference for human readers, search systems, and language models. Major region: Gulf / Atlantic Regional setting: Northern Gulf Coastal Plain uplands Age: Pliocene to possible early Pleistocene Age detail: Generally treated as Pliocene, with long-running regional debate over its upper age limit Depositional setting: Broad river systems, alluvial uplands, and locally coastal environments Rock types: Sand, Gravel, Silt, Clay States in recognized usage: Alabama, Florida, Louisiana, Mississippi ## Summary The Citronelle Formation is a weathered blanket of sand, gravel, silt, and clay across Gulf Coastal Plain uplands, recording large late Neogene river systems and a still-debated age. ## Distribution Citronelle deposits cap broad uplands from Mississippi and Alabama into the Florida Panhandle, with related usage in Louisiana. Younger terraces cut below or overlap its margins, and older Coastal Plain formations lie beneath an erosional contact. Its mapped limits and correlation have changed because deeply weathered sand and gravel can resemble younger terrace deposits. Some areas historically called Citronelle may not belong to the same depositional episode. ## Geological history Large rivers deposited cross-bedded sand and gravel, with quieter floodplain or abandoned-channel settings preserving silt and clay. Some Florida sections may include nearshore influence. Long weathering produced red and orange iron coatings, kaolinite-rich clay, and resistant iron-cemented horizons. Erosion later dissected the once broader upland surface. ## Fossil record Fossils are sparse and usually not diagnostic. Plant remains, pollen, and rare vertebrate evidence have contributed to competing Pliocene and Pleistocene age interpretations. The limited fossil record means age is commonly inferred from regional position, weathering, and correlation. A single isolated fossil or gravel clast cannot resolve the formation’s age. ## Minerals and geological resources Quartz dominates sand and gravel, while kaolinite and illite are important clay minerals. Hematite, goethite, manganese oxides, and locally gibbsite occur in weathering coatings or cement. Sand and gravel are local construction resources. Iron-cemented layers and clay lenses strongly influence drainage, slope stability, and shallow groundwater. ## Field context - Red sand and gravel alone are not sufficient for identification because younger terraces can look similar. - Borrow pits and quarries require permission and may have unstable faces or equipment traffic. - Age and regional correlations remain scientifically qualified rather than fixed everywhere. ## Connected field guides - Goethite (mineral; Mineral discussed in this formation) — https://lithomap.app/resources/mineral-identification/goethite - Hematite (mineral; Mineral discussed in this formation) — https://lithomap.app/resources/mineral-identification/hematite - Kaolinite (mineral; Mineral discussed in this formation) — https://lithomap.app/resources/mineral-identification/kaolinite - Quartz (mineral; Mineral discussed in this formation) — https://lithomap.app/resources/mineral-identification/quartz Mapped location and formation context support an identification but cannot establish one. Compare several physical properties and use laboratory analysis when the material remains ambiguous. ## Connected state geology guides - Florida geology — https://lithomap.app/resources/geology/united-states/florida ## Authoritative sources - Geolex Citronelle references — U.S. Geological Survey: https://ngmdb.usgs.gov/Geolex/UnitRefs/CitronelleRefs_1073.html - Quaternary map of the Mobile region — U.S. Geological Survey: https://pubs.usgs.gov/publication/i1420NH16 ## Formation photograph - Image: https://lithomap.app/_delivery/formations/citronelle-formation.webp - Description: Iron-stained Citronelle Formation sandstone with an Ophiomorpha burrow in Pensacola, Florida - Creator: James St. John - License: CC BY 2.0 — https://creativecommons.org/licenses/by/2.0/ - Source record: https://commons.wikimedia.org/wiki/File:Iron_oxide-stained%2C_poorly_indurated_clayey_sandstone_with_Ophiomorpha_burrow_(Citronelle_Formation%2C_Pliocene%3B_Bay_Bluffs_Park%2C_Pensacola%2C_Florida%2C_USA).jpg Formation-level information does not prove that a fossil or mineral occurs at a specific coordinate. It also does not establish ownership, access, collecting permission, present conditions, or specimen identity.